Absorbent structures having enhanced flexibility

ABSTRACT

Absorbent structures suitable for incorporation into disposable absorbent articles. Specifically, non-woven absorbent structures having a unitary construction and comprising absorbent fibers, a portion of the absorbent structure having discontinuous absorbent zones that define channels. The absorbent structures having the discontinuous absorbent zones demonstrating an enhanced flexibility.

BACKGROUND

The present invention relates to absorbent structures suitable forincorporation into disposable absorbent articles. More particularly, thepresent invention relates to non-woven absorbent structures havingenhanced flexibility.

Stabilized absorbent structures are gaining favor among manufactures ofdisposable absorbent articles. However, many of these stabilizedabsorbent structures are perceived as lacking in flexibility.Consequently, there remains a need to enhance the flexibility ofstabilized absorbent structures.

SUMMARY

In response to the foregoing need, the present inventors conductedintensive research and development efforts that resulted in thediscovery of unique absorbent structures having enhanced flexibility.The present inventors were further surprised that their discovery couldalso enhance the flexibility of conventional non-stabilized absorbentstructures. Specifically, one version of the present invention providesfor an absorbent body suitable for incorporation into a disposableabsorbent article. The absorbent body includes a non-woven absorbentstructure having a unitary construction and absorbent fibers. Theabsorbent structure has a longitudinal length, a lateral width and athickness. At least a portion of the absorbent structure hasdiscontinuous absorbent zones that define at least two channels. In thisversion, at least one of the channels runs in a longitudinal lengthdirection of the absorbent structure. Also in this version, at least oneof the channels runs in a lateral width direction of the absorbentstructure. The density of the absorbent structure in the channels isless than or equal to the density of a portion of the absorbentstructure adjacent the channels.

Another version of the present invention provides for an absorbentarticle comprising a fluid pervious liner, a liquid impervious outercover and an absorbent body. The absorbent body is disposed between theliner and the outer cover. The absorbent body includes a non-wovenabsorbent structure having a unitary construction and absorbent fibers.The absorbent structure has a longitudinal length, a lateral width and athickness. At least a portion of the absorbent structure hasdiscontinuous absorbent zones that define at least two channels. In thisversion, at least one of the channels runs in a longitudinal lengthdirection of the absorbent structure. Also in this version, at least oneof the channels runs in a lateral width direction of the absorbentstructure. The density of the absorbent structure in the channels isless than or equal to the density of a portion of the absorbentstructure adjacent the channels.

Still another version of the present invention provides for an absorbentbody suitable for incorporation into a disposable absorbent article. Theabsorbent body includes a non-woven absorbent structure having a unitaryconstruction and absorbent fibers. The absorbent structure has alongitudinal length, a lateral width and a thickness. At least a portionof the absorbent structure has discontinuous absorbent zones that defineat least four channels. In this version, at least two of the channelsrun in a longitudinal length direction of the absorbent structure. Alsoin this version, at least two of the channels run in a lateral widthdirection of the absorbent structure. The density of the absorbentstructure in the channels is less than or equal to the density of aportion of the absorbent structure adjacent the channels. That portionof the absorbent structure having the discontinuous absorbent zones hasa cylindrical compression at yield which is at least 55 percent lessthan the cylindrical compression at yield of an otherwise similarabsorbent structure free of the discontinuous absorbent zones.

DRAWINGS

The foregoing and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings where:

FIG. 1 is a plan view of an absorbent article of the present inventionillustrated in the form of a diaper shown unfastened and laid flat;

FIG. 2 is an exploded cross section taken generally in the planeincluding line 2-2 of FIG. 1;

FIG. 3 is a perspective view of the diaper shown as worn;

FIG. 4 is a longitudinal cross-section of an absorbent structure of thediaper of FIG. 1 taken generally on the longitudinal axis thereof;

FIG. 5 is a schematic perspective of an apparatus for forming anabsorbent structure of the present invention;

FIG. 6 is an enlarged side elevation of an airforming device of theapparatus of FIG. 5;

FIG. 7 is a fragmentary cross-section of the airforming device of FIG.6;

FIG. 8 is a schematic perspective of a forming drum and forming surfaceof the airforming device of FIG. 6;

FIG. 9 is an enlarged schematic of a portion of the forming drum andforming surface;

FIG. 10 is a schematic perspective of a longitudinal cross-section takenthrough a portion of the forming drum and forming surface;

FIG. 11 representatively illustrates an absorbent structure, a portionof which has discontinuous absorbent zones that define channels;

FIG. 12 representatively illustrates an absorbent structure, a portionof which has discontinuous absorbent zones that define channels;

FIG. 13 representatively illustrates an example of a formed grid; and

FIG. 14 representatively illustrates an example of a wire grid.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION

Referring now to the drawings and in particular to FIG. 1, one exampleof an absorbent article incorporating the present invention isillustrated in the form of a diaper, which is indicated in its entiretyby the reference numeral 21. As used herein, an absorbent article refersto an article which may be placed against or in proximity to the body ofthe wearer (e.g., contiguous to the body) to absorb and/or retainvarious waste discharged from the body. Some absorbent articles, such asdisposable absorbent articles, are intended to be discarded after alimited period of use instead of being laundered or otherwise restoredfor reuse. It is contemplated, however, that the principles of thepresent invention have application in garments (including reusablegarments) and other absorbent articles. For example, the principles ofthe present invention may be incorporated into children's training pantsand other infant and child care products, adult incontinence garmentsand other adult care products, medical garments, sanitary napkins andother feminine care products and the like, as well as surgical bandagesand sponges.

The diaper 21 is shown in FIG. 1 in an unfolded and laid-flat conditionto illustrate a longitudinal axis X and a lateral axis Y of the diaper.The diaper 21 generally comprises a central absorbent assembly 23extending longitudinally from a front (e.g., anterior) region 25 of thediaper through a crotch (e.g., central) region 27 to a back (e.g.,posterior) region 29 of the diaper. The central absorbent assembly 23 isgenerally I-shaped, and more particularly hourglass shaped, and hascontoured, laterally opposite side edges 31 and longitudinally oppositefront and rear waist edges or ends, respectively designated 33 and 35.It is understood, however, that the diaper 21 may have other shapes,such as a rectangular shape or a T-shape without departing from thescope of the present invention. The side edges 31 of the diaper 21extend longitudinally from the front region 25 through the crotch region27 to the back region 29 for forming transversely spaced leg openings 37(FIG. 3) of the diaper when worn.

The front region 25 generally includes the portions of the centralabsorbent assembly 23 which extend over the wearer's lower abdominalregion and the back region 29 generally includes the portions of thecentral absorbent assembly which extend over the wearer's lower backregion. The crotch region 27 includes the portion extendinglongitudinally through the wearer's crotch from the front region 25 tothe back region 29 and laterally between the wearer's legs. As worn onthe wearer's body (FIG. 3), the diaper 21 further defines a centralwaist opening 43 and the leg openings 37.

With particular reference to FIG. 2, the central absorbent assembly 23of the diaper 21 comprises an outer cover, generally indicated at 49, abodyside liner 51 positioned in facing relation with the outer cover,and an absorbent body, generally indicated at 53, disposed between theouter cover and the liner. The outer cover 49 of the illustratedembodiment generally defines the length and width of the diaper 21. Theabsorbent body 53 has a length and width which are less than therespective length and width of the outer cover 49 such that the outercover extends both longitudinally and laterally out beyond the sides andends of the absorbent body. The bodyside liner 51 may be generallycoextensive with the outer cover 49, or may instead overlie an areawhich is larger (and would thus generally define the length and/or widthof the diaper 21) or smaller than the area of the outer cover 49, asdesired. In other words, the bodyside liner 51 is desirably insuperposed relation with the outer cover 49 but may not necessarily becoextensive with the outer cover.

In one embodiment, the outer cover 49 is stretchable and may or may notbe somewhat elastic. More particularly, the outer cover 49 issufficiently extensible such that once stretched under the weight of theinsulted absorbent body, the outer cover will not retract substantiallyback toward its original position. However, it is contemplated that theouter cover 49 may instead be generally non-extensible and remain withinthe scope of this invention.

The outer cover 49 may be a multi-layered laminate structure to providedesired levels of extensibility as well as liquid impermeability andvapor permeability. For example, the outer cover 49 of the illustratedembodiment is of two-layer construction, including an outer layer 55constructed of a vapor permeable material and an inner layer 57constructed of a liquid impermeable material, with the two layers beingsecured together by a suitable laminate adhesive 59. It is understood,however, that the outer cover 49 may instead be constructed of a singlelayer of liquid impermeable material, such as a thin plastic filmconstructed of materials such as those from which the inner layer 57 isconstructed as described later herein, without departing from the scopeof this invention. The liquid impermeable inner layer 57 of the outercover 49 can be either vapor permeable (i.e., “breathable”) or vaporimpermeable.

The bodyside liner 51 is preferably pliable, soft feeling, andnonirritating to the wearer's skin, and is employed to help isolate thewearer's skin from the absorbent body 53. The liner 51 is lesshydrophilic than the absorbent body 53 to present a relatively drysurface to the wearer, and is sufficiently porous to be liquid permeableto thereby permit liquid to readily penetrate through its thickness. Asuitable bodyside liner 51 may be manufactured from a wide selection ofweb materials, but is preferably capable of stretching in at least onedirection (e.g., longitudinal or lateral). In particular embodiments,the bodyside liner 51 is desirably extensible and capable of extendingalong with the outer cover 49 for desired fit of the diaper on thewearer.

Fastener tabs 65 (FIGS. 1 and 3) are secured to the central absorbentassembly 23 generally at the back region 29 thereof with the tabsextending laterally out from the opposite side edges 31 of the assembly.The fastener tabs 65 may be attached to the outer cover 49, to thebodyside liner 51, between the outer cover and liner, or to othercomponents of the diaper 21. The tabs 65 may also be elastic orotherwise rendered elastomeric. For example, the fastener tabs 65 may bean elastomeric material such as a neck-bonded laminate (NBL) orstretch-bonded laminate (SBL) material.

Methods of making such materials are well known to those skilled in theart and are described in U.S. Pat. No. 4,663,220 issued May 5, 1987 toWisneski et al., U.S. Pat. No. 5,226,992 issued Jul. 13, 1993 to Morman,and European Patent Application No. EP 0 217 032 published on Apr. 8,1987 in the names of Taylor et al., the disclosures of which are herebyincorporated by reference. Examples of articles that include selectivelyconfigured fastener tabs are described in U.S. Pat. No. 5,496,298 issuedMar. 5, 1996 to Kuepper et al.; U.S. Pat. No. 5,540,796 to Fries; andU.S. Pat. No. 5,595,618 to Fries; the disclosures of which are alsoincorporated herein by reference. Alternatively, the fastener tabs 65may be formed integrally with a selected diaper component. For example,the tabs 65 may be formed integrally with the inner or outer layer 57,55 of the outer cover 49, or with the bodyside liner 51.

Fastening components, such as hook and loop fasteners, designated 71 and72 respectively, are employed to secure the diaper 21 on the body of achild or other wearer. Alternatively, other fastening components (notshown), such as buttons, pins, snaps, adhesive tape fasteners,cohesives, mushroom-and-loop fasteners, or the like, may be employed.Desirably, the interconnection of the fastening components 71, 72 isselectively releasable and re-attachable. In the illustrated embodiment,the hook fasteners 71 are secured to and extend laterally out from therespective fastener tabs 65 at the back region 29 of the diaper 21.However, it is understood that the fastener tabs 65 may be formed of ahook material and thus comprise the hook fasteners 71 without departingfrom the scope of this invention. The loop fastener 72 of theillustrated embodiment is a panel of loop material secured to the outercover 49 at the front region 25 of the diaper 21 to provide a “fastenanywhere” mechanical fastening system for improved fastening of the hookfasteners 71 with the loop fastener.

The loop material may include a pattern-unbonded non-woven fabric havingcontinuous bonded areas that define a plurality of discrete unbondedareas. The fibers or filaments within the discrete unbonded areas of thefabric are dimensionally stabilized by the continuous bonded areas thatencircle or surround each unbonded area, such that no support or backinglayer of film or adhesive is required. The unbonded areas arespecifically designed to afford spaces between fibers or filamentswithin the unbonded areas that remain sufficiently open or large toreceive and engage hook elements of the complementary hook fasteners 71.In particular, a pattern-unbonded non-woven fabric or web may include aspunbond non-woven web formed of single component or multi-componentmelt-spun filaments. For example, the loop material may be a laminatedstructure including a polyethylene component and a polypropylenecomponent adhesively bonded together with the polypropylene componentfacing outward away from the outer cover 49 to receive the hookfasteners 71. Examples of suitable pattern-unbonded fabrics aredescribed in U.S. Pat. No. 5,858,515 issued Jan. 12, 1999 to T. J.Stokes et al. and entitled PATTERN-UNBONDED NON-WOVEN WEB AND PROCESSFOR MAKING THE SAME; the entire disclosure of which is incorporatedherein by reference in a manner that is consistent herewith.

The diaper 21 shown in FIG. 1 also comprises a pair of containmentflaps, generally indicated at 75, configured to provide a barrier to thelateral flow of body exudates. The containment flaps 75 are locatedgenerally adjacent the laterally opposite side edges 31 of the diaper 21and, when the diaper is laid flat as shown in FIGS. 1 and 2, extendinward toward the longitudinal axis X of the diaper. Each containmentflap 75 typically has a free, or unattached end 77 free from connectionwith the bodyside liner 51 and other components of the diaper 21.Elastic strands 79 disposed within the flaps 75 adjacent the unattachedends thereof urge the flaps toward an upright, perpendicularconfiguration in at least the crotch region 27 of the diaper 21 to forma seal against the wearer's body when the diaper is worn. Thecontainment flaps 75 may extend longitudinally the entire length of theabsorbent body 53 or they may extend only partially along the length ofthe absorbent body. When the containment flaps 75 are shorter in lengththan the absorbent body 53, the flaps can be selectively positionedanywhere between the side edges 31 of the diaper 21 in the crotch region27. In a particular aspect of the invention, the containment flaps 75extend the entire length of the absorbent body 53 to better contain thebody exudates.

Such containment flaps 75 are generally well known to those skilled inthe art and therefore will not be further described herein except to theextent necessary to describe the present invention. As an example,suitable constructions and arrangements for containment flaps 75 aredescribed in U.S. Pat. No. 4,704,116 issued Nov. 3, 1987, to K. Enloe,the disclosure of which is hereby incorporated by reference. The diaper21 may also incorporate other containment components in addition to orinstead of the containment flaps 75. For example, while not shown in thedrawings, other suitable containment components may include, but are notlimited to, elasticized waist flaps, foam dams in the front, back and/orcrotch regions, and the like.

The various components of the diaper 21 are assembled together using asuitable form of attachment, such as adhesive, sonic bonds, thermalbonds or combinations thereof. In the illustrated embodiment, the outercover 49 and absorbent body 53 are secured to each other with lines ofadhesive 81, such as a hot melt or pressure-sensitive adhesive. Thebodyside liner 51 is also secured to the outer cover 49 and may also besecured to the absorbent body 53 using the same forms of attachment.

The bodyside liner 51 may be secured to the outer cover 49 at thelateral edge margins of the crotch region 27, but at least the centralportion is free of such connection. Rather than being entirely free ofsuch connection, the bodyside liner 51 may be secured to the absorbentbody 53 in the crotch region 27 by a light adhesive 83 which will breakaway in use. Preferably, securement of the bodyside liner 51 to theouter cover 49 is limited to overlying peripheral edge margins of thetwo to promote independent stretching movement of the liner and coverrelative to each other. If the diaper 21 is to be sold in a pre-fastenedcondition, the diaper may also have passive bonds (not shown) which jointhe back region 29 with the front region 25.

The diaper 21 can also include a surge management layer (not shown)which helps to decelerate and diffuse surges or gushes of liquid thatmay be rapidly introduced into the absorbent body 53. Desirably, thesurge management layer can rapidly accept and temporarily hold theliquid prior to releasing the liquid to the absorbent structure. In theillustrated embodiment, for example, a surge layer can be locatedbetween the absorbent body 53 and the bodyside liner 51. Examples ofsuitable surge management layers are described in U.S. Pat. No.5,486,166 entitled FIBROUS NON-WOVEN WEB SURGE LAYER FOR PERSONAL CAREABSORBENT ARTICLES AND THE LIKE by C. Ellis and D. Bishop, which issuedJan. 23, 1996, and U.S. Pat. No. 5,490,846 entitled IMPROVED SURGEMANAGEMENT FIBROUS NON-WOVEN WEB FOR PERSONAL CARE ABSORBENT ARTICLESAND THE LIKE by C. Ellis and R. Everett, which issued Feb. 13, 1996, theentire disclosures of which are hereby incorporated by reference in amanner that is consistent herewith.

To provide improved fit and to help further reduce leakage of bodyexudates from the diaper 21, elastic components are typicallyincorporated therein, particularly at the waist area and the leg areas.For example, the diaper 21 of the illustrated embodiment has waistelastic components 85 (FIG. 3) and leg elastics 87 (FIGS. 1 and 2). Thewaist elastic components 85 are configured to gather and shirr the endmargins of the diaper 21 to provide a resilient, comfortable close fitaround the waist of the wearer and the leg elastics 87 are configured togather and shirr the side margins of the diaper at the leg openings 37to provide a close fit around the wearer's legs.

Examples of other diaper 21 configurations suitable for use inconnection with the instant application that may or may not includediaper components similar to those described previously are described inU.S. Pat. No. 4,798,603 issued Jan. 17, 1989, to Meyer et al.; U.S. Pat.No. 5,176,668 issued Jan. 5, 1993, to Bemardin; U.S. Pat. No. 5,176,672issued Jan. 5, 1993, to Bruemmer et al.; U.S. Pat. No. 5,192,606 issuedMar. 9, 1993, to Proxmire et al., U.S. Pat. No. 5,509,915 issued Apr.23, 1996 to Hanson et al., U.S. Pat. No. 5,993,433 issued Nov. 30, 199to St. Louis et al., and U.S. Pat. No. 6,248,097 issued Jun. 19, 2001 toBeitz et al., the disclosures of which are herein incorporated byreference.

In accordance with one version of the present invention, the absorbentbody 53 at least in part comprises a stabilized non-woven absorbentstructure 101 (FIG. 4) formed from a mixture of absorbent fibers andbinder fibers (broadly, a binding material) which are activatable aswill be described to form inter-fiber bonds within the absorbentstructure for stabilizing the absorbent structure. Optionally,superabsorbent material may be included in the mixture from which thestabilized non-woven absorbent structure 101 is formed. The absorbentfibers may be provided by various types of wettable, hydrophilic fibrousmaterial. For example, suitable absorbent fibers include naturallyoccurring organic fibers composed of intrinsically wettable material,such as cellulosic fibers; synthetic fibers composed of cellulose orcellulose derivatives, such as rayon fibers; inorganic fibers composedof an inherently wettable material, such as glass fibers; syntheticfibers made from inherently wettable thermoplastic polymers, such asparticular polyester or polyamide fibers; and synthetic fibers composedof a nonwettable thermoplastic polymer, such as polypropylene fibers,which have been hydrophilized by appropriate means. The fibers may behydrophilized, for example, by treatment with silica, treatment with amaterial that has a suitable hydrophilic moiety and is not readilyremovable from the fiber, or by sheathing the nonwettable, hydrophobicfiber with a hydrophilic polymer during or after the formation of thefiber. For the present invention, it is contemplated that selectedblends of the various types of fibers mentioned above may also beemployed.

Suitable sources of absorbent fibers may include cellulosic fibersincluding: wood fibers, such as bleached kraft softwood or hardwood,high-yield wood fibers, and ChemiThermoMechanical Pulp fibers; bagassefibers; milkweed fluff fibers; wheat straw; kenaf; hemp; pineapple leaffibers; or peat moss. High-yield fibers, such as Bleached ChemiThermalMechanical Pulp (BCTMP) fibers, can be flash-dried and compressed intodensified pads. The high-yield fiber can expand to a higher loft whenwetted, and can be used for the absorbent fiber material. Otherabsorbent fibers, such as regenerated cellulose and curled chemicallystiffened cellulose fibers may also be densified to form absorbentstructures that can expand to a higher loft when wetted.

As an example, suitable wood pulps include standard softwood fluffinggrade such as NB-416 (Weyerhaeuser Corporation, Tacoma, Wash., U.S.A.)and CR-1654 (US Alliance Pulp Mills, Coosa, Ala., U.S.A.), bleachedkraft softwood or hardwood, high-yield wood fibers,ChemiThermoMechanical Pulp fibers and BCTMP fibers. Pulp may be modifiedin order to enhance the inherent characteristics of the fibers and theirprocessability. Curl may be imparted to the fibers by conventionalmethods including chemical treatment or mechanical twisting. Pulps mayalso be stiffened by the use of crosslinking agents such as formaldehydeor its derivatives, glutaraldehyde, epichlorohydrin, methylolatedcompounds such as urea or urea derivatives, dialdehydes such as maleicanhydride, non-methylolated urea derivatives, citric acid or otherpolycarboxylic acids. Some of these agents are less preferable thanothers due to environmental and health concerns.

Pulp may also be stiffened by the use of heat or caustic treatments suchas mercerization. Examples of these types of fibers include NHB416 whichis a chemically crosslinked southern softwood pulp which enhances wetmodulus, available from the Weyerhaeuser Corporation of Tacoma, Wash.,U.S.A. Other useful pulps are debonded pulp (NF405) also fromWeyerhaeuser. HPZ3 from Buckeye Technologies, Inc of Memphis, Term.,U.S.A., has a chemical treatment that sets in a curl and twist, inaddition to imparting added dry and wet stiffness and resilience to thefiber. Another suitable pulp is Buckeye HPF2 pulp and still another isIP SUPERSOFT® from International Paper Corporation. Suitable rayonfibers include 1.5 denier Merge 18453 fibers from Tencel Incorporated ofAxis, Ala., U.S.A.

The binder fibers are desirably activatable, such as upon being heated,to form inter-fiber bonds within the absorbent structure. As usedherein, the inter-fiber bonds may be between the binder fibers and theabsorbent fibers, between the binder fibers and the superabsorbentmaterial, and/or among the binder fibers themselves.

In one embodiment, the binder fibers are bicomponent, or multicomponentbinder fibers. As used herein, multicomponent fibers refers to fibersformed from two (e.g., bicomponent) or more polymers extruded fromseparate extruders but joined together to form a single fiber. Thepolymers are arranged in substantially constantly positioned distinctzones across a cross-section of the multi-component fibers and extendcontinuously along at least a portion of, and more desirably the entire,length of the fiber. The configuration of the multi-component fibers maybe, for example, a sheath/core arrangement in which one polymer issurrounded by another, a side-by-side arrangement, a pie arrangement, an“islands-in-the-sea” arrangement or other suitable arrangement.Bicomponent fibers are disclosed in U.S. Pat. No. 5,108,820 to Kaneko etal., U.S. Pat. No. 4,795,668 to Krueger et al., U.S. Pat. No. 5,540,992to Marcher et al. and U.S. Pat. No. 5,336,552 to Strack et al.Bicomponent fibers are also taught in U.S. Pat. No. 5,382,400 to Pike etal. and may be used to produce crimp in the fibers by using thedifferential rates of expansion and contraction of the two (or more)polymers.

Multicomponent binder fibers as used herein refers to multicomponentfibers in which at least one of the binder fiber components has a melttemperature that is less than at least one other binder fiber component.For example, the binder fiber may be a bicomponent fiber having asheath/core arrangement in which the sheath component of the binder hasa melt temperature that is lower than the melt temperature of the corecomponent of the binder fiber. Upon heating of the binder fiber, thecomponent having the lower melt temperature can fuse and bond to nearbyabsorbent fibers, superabsorbent material or other binder fibers whilethe other component, or components, remain in a generally unmelted stateso as to generally maintain the integrity of the binder fiber.

In other embodiments, the binder fibers can be monofilament orhomofilament fibers, biconstituent fibers and the like, as well ascombinations thereof.

The binder fibers are desirably constructed of a material, or material,that are readily heated upon exposure to an activation energy, and moreparticularly the binder fibers are desirably susceptible to dielectricheating via exposure to electromagnetic energy wherein the binder fibersare melted to facilitate forming inter-fiber bonds within the absorbentstructure.

Superabsorbent materials useful in forming the absorbent structure 101may be chosen based on chemical structure as well as physical form.These include superabsorbent materials with low gel strength, high gelstrength, surface cross-linked superabsorbent materials, uniformlycross-linked superabsorbent materials, or superabsorbent materials withvaried cross-link density throughout the structure 101. Thesuperabsorbent materials may be based on chemistries that includepoly(acrylic acid), poly(iso-butylene-co-maleic anhydride),poly(ethylene oxide), carboxy-methyl cellulose, poly(-vinylpyrrollidone), and poly(-vinyl alcohol). The superabsorbent materialsmay range in swelling rate from slow to fast.

The superabsorbent materials of the absorbent structure 101 of thepresent invention are desirably particulate. However, the superabsorbentmaterials may alternatively be in the form of foams, macroporous ormicroporous particles or fibers, particles or fibers with fibrous orparticulate coatings or morphology. The superabsorbent materials may bein various length and diameter sizes and distributions and may also bein various degrees of neutralization. Counter-ions are typically Li, Na,K, Ca.

An exemplary superabsorbent material is available from Stockhausen,Inc., of Greensboro, N.C., U.S.A. and is designated FAVOR® SXM 880.Another examplary superabsorbent material may be obtained from The DowChemical Co. of Midland, Mich., U.S.A. under the name DRYTECH® 2035. Asuitable fibrous superabsorbent material is available from CamelotTechnologies, Ltd., of High River, Alberta, Canada and is designatedFIBERDRI® 1241. Another suitable superabsorbent material is availablefrom Chemtall Inc. of Riceboro, Ga., and is designated FLOSORB 60 LADY®,also known as LADYSORB 60®.

Dielectric heating is the term applied to the generation of heat innon-conducting materials by their losses when subject to an alternatingelectric field of high frequency. For example, the frequency of theelectric field desirably ranges from about 0.01 to about 300 GHz(billion cycles/sec). Heating of non-conductors by this method isextremely rapid. This form of heating is applied by placing thenon-conducting material between two electrodes, across which thehigh-frequency voltage is applied. This arrangement in effectconstitutes an electric capacitor, with the load acting as thedielectric. Although ideally a capacitor has no losses, practical lossesdo occur, and sufficient heat is generated at high frequencies to makethis a practical form of heat source.

The frequency used in dielectric heating is a function of the powerdesired and the size of the object being heated. Practical values ofvoltages applied to the electrodes are 2000 to 5000 volts/in ofthickness of the object. The source of power is by electronicoscillators that are capable of generating the very high frequenciesdesirable.

The basic requirement for dielectric heating is the establishment of ahigh-frequency alternating electric field within the material or objectto be heated. Once the electric field has been established, the secondrequirement involves dielectric loss properties of the material to beheated. The dielectric loss of a given material occurs as a result ofelectrical polarization effects in the material itself and may bethrough dipolar molecular rotation and ionic conduction. The higher thedielectric loss of a material, the more receptive to the high frequencyenergy it is.

In one embodiment, the electromagnetic energy is radio frequency or RFradiation, which occurs at about 27 MHz and heats by providing someportion of the total power delivered as ionic conduction to themolecules within the workpiece, with much of the remainder of the powerdelivered as dipolar molecular rotation.

In another embodiment, the electromagnetic energy is microwaveradiation, which is dielectric heating at still higher frequencies. Thepredominate frequencies used in microwave heating are 915 and 2450 MHz.Microwave heating is 10 to 100 times higher in frequency than the usualdielectric heating, resulting in a lower voltage requirement if the lossfactor is constant, though the loss factor is generally higher atmicrowave frequencies.

Microwave radiation can penetrate dielectric materials and be absorbeduniformly, thereby generating heat uniformly. Microwave energy is alsoselectively absorbed, offering a means for self-limiting the energytaken up by heterogeneous materials, making overheating less likely.These combined effects allow microwave heating to be more rapid, withless heating of surrounding materials, with a low thermal lag, andtherefore with good control.

It is understood that the binder fibers or other suitable bindingmaterial may be activatable other than by dialectric heating, such as byconvective or infrared heating or other non-thermal activation, as longas the binder fibers can be incorporated into the absorbent structure101 prior to activation of the binder fibers to form inter-fiber bondswithin the absorbent structure and then subsequently activated to formsuch inter-fiber bonds to thereby form the stabilized absorbentstructure 101.

The binder fibers desirably have a fiber length which is at least about0.061 mm. The binder fiber length can alternatively be at least about 3mm and can optionally be at least about 6 mm. In a further feature, thebinder-fibers can have a length of up to about 30 mm or more. The binderfiber length can alternatively be up to about 25 mm, and can optionallybe up to about 19 mm. In a further aspect, the absorbent structure 101may include binder fibers having lengths approximating one of thedimensions (e.g., length or width) of the absorbent structure. Arelatively long binder fiber length provides an increased number ofinter-fiber bond points upon activation of the fibers to help generateimproved integrity and permeability of the absorbent structure 101.

Synthetic fibers suitable for use as binder fibers in the absorbentstructure 101 include those made from synthetic matrix polymers likepolyolefins, polyamides, polycaprolactones, polyetheramides,polyurethanes, polyesters, poly(meth)acrylates metal salts, polyether,poly(ethylene-vinyl acetate) random and block copolymers,polyethylene-b-polyethylene glycol block copolymers, polypropyleneoxide-b-polyethylene oxide copolymers (and blends thereof) and any othersuitable synthetic fibers known to those skilled in the art.

In one embodiment, an energy receptive additive can be included in thebinder fibers during production thereof wherein the additive allows thebinder fibers to reach their melting temperature much more rapidly thanwithout the additive. This allows inter-fiber bonding in the absorbentstructure 101 to occur at a faster rate than without the additive. Theadditive is desirably capable of absorbing energy at the frequency ofelectromagnetic energy (e.g., between 0.01 GHz and 300 GHz) rapidly,such as in the range of fractions of a second, desirably less than aquarter of a second and at most about half a second. However, it iscontemplated that absorbent structures which involve the absorption ofenergy and bonding of the binder fibers with the absorbent fibers over aperiod as long as about 30 seconds are intended to be within the scopeof this invention. Melting of the binder fibers will depend on a numberof factors such as generator power, additive receptivity, fiber denier,which is generally between 1 and 20, and the composition of the matrixpolymer of the binder fiber.

The energy receptive additive may be added to a fiber-making matrixpolymer as it is compounded, or coated onto the binder fiber after thefiber is produced. A typical method of compounding the additive with thematrix polymer is with a twin screw extruder, which thoroughly mixes thecomponents prior to extruding them. Upon extrusion, the polymer blend isusually pelletized for convenient storage and transportation.

If the binder fiber is a bicomponent fiber, the energy receptiveadditive may be added to either or both of the fiber components. Theenergy receptive additive may also be added to one or more components,preferably the continuous phase, of a biconstituent fiber, andintermittently distributed throughout the length and cross-section ofthe fiber. If the additive to be used is not compatible with the matrixpolymer into which it is to be blended, a “compatibilizer” may be addedto enhance the blending. Such compatibilizers are known in the art andexamples may be found in U.S. Pat. Nos. 5,108,827 and 5,294,482 toGessner.

The energy receptive additives can be receptive to various specificspectra of energy. Just as a black item will absorb more energy andbecome warmer than the same item colored white when subjected to thesame amount of solar energy, energy receptive additives will absorbenergy at their specific wavelength, directed at them.

A successful energy receptive additive should have a dielectric lossfactor, as discussed previously, which is relatively high. The energyreceptive additives useful in this invention typically can have adielectric loss factor measured in the RF or microwave frequency ofbetween about 0.5 and 15, more particularly between about 1 and 15, andstill more particularly between about 5 and 15. It should be noted thatthe dielectric loss factor is a dimensionless number. It is preferredthat the fiber have a dielectric loss tangent of between about 0.1 andabout 1, and more particularly between about 0.3 and about 0.7.

The energy receptive additive may be, for example, carbon black,magnetite, silicon carbide, calcium chloride, zircon, alumina, magnesiumoxide, and titanium dioxide. The energy receptive additive may bepresent in an amount between 2 and 40 weight percent, and moreparticularly between 5 and 15 weight percent. The binder fibers may becrimped, extendible and/or elastic.

Synthetic fibers incorporating such energy receptive additives arediscussed at greater length in U.S. patent application Ser. No.10/034,079 filed Dec. 20, 2001 and entitled Targeted Bonding Fibers forStabilized Absorbent Structures, the entire disclosure of which isincorporated herein by reference. Absorbent structures incorporatingbinder fibers having such energy receptive additives are discussed inU.S. patent application Ser. No. 10/033,860 filed Dec. 20, 2001 andentitled Targeted On-Line Stabilized Absorbent Structures.

In addition to the binder fibers having an energy receptive additive, oras an alternative thereto, the binder fibers (or at least one binderfiber component thereof where the binder fiber is a multicomponentfiber) may be constructed to have a relatively low melting temperature,such as less than about 200° C., more desirably less than about 150° C.,even more desirably less than about 110° C., still more desirably lessthan about 90° C., and most desirably less than about 80° C. In such aninstance, the absorbent fibers and superabsorbent material of theabsorbent structure 101 can act as a source of heat to indirectlytransfer energy to melt the low melting temperature binder fibers. Theabsorbent fibers thus act as an energy receptive material, and areexcited to melt the adjacent low melting temperature polymers of thebinder fibers for bonding to the absorbent fibers, to the superabsorbentmaterial and/or to each other. This melting will depend on a number offactors such as generator power, moisture content, specific heat,density of the absorbent structure 101 materials, fiber denier, which isgenerally between 1 and 20, and the composition and concentration of thelow melting temperature polymers of the binder fibers.

The low melting temperature binder fibers desirably have a low specificheat to allow rapid heating and cooling of the absorbent structure 101.The low specific heat is useful during the heating cycle since the heatabsorbed by the binder fiber before melting is relatively low. The lowspecific heat is also useful during subsequent cooling of the absorbentstructure 101, since the heat to be removed from the binder fibermaterial to cause it to solidify and stabilize the absorbent structurewill be lower. A suitable specific heat range of the binder fiber is inthe range of about 0.1 to about 0.6 calories/gram.

The binder fibers also desirably have a high thermal conductivity toenable rapid transfer of heat therethrough. Thermal conductivity isproportional to density and heat capacity/specific heat capacity of thebinder fiber material. It is beneficial to achieve higher thermalconductivity using fibers with relatively high density. For example, thebinder fibers desirably have a density of more than about 0.94grams/cubic centimeter (g/cc). This is helpful in accelerating theheating and cooling cycles during activation of the binder fibers tostabilize the absorbent structure 101. It is preferred that the thermalconductivity of the binder fibers be greater than about 0.1joules-sec⁻¹-mole⁻¹-degree Kelvin⁻¹.

Materials having a low melting enthalpy are also desirable for use asthe binder fibers. The low melting enthalpy reduces the energyrequirement for transformation of the binder fiber from a solid to amolten state during heating thereof and from the molten state back to asolid state during subsequent cooling. As an example, the meltingenthalpy of the binder fibers is desirably less than about 100joules/gram, more particularly less than about 75 joules/gm and stillmore particularly less than about 60 joules/gm.

The binder fibers also desirably have a low melt viscosity afteractivation, i.e., once the fiber is transformed from its solid to itsgenerally molten state. This enables the binder fiber material to flowto the junction points between the binder fibers and the absorbentfibers, superabsorbent material and/or other binder fibers for formingstable inter-fiber bonds. As an example, it is desired that the meltviscosity of the binder fibers be less than about 100,000 centipoise,more particularly less than about 20,000 centipoise and mostparticularly less than about 10,000 centipoise.

The binder fibers also desirably have adequate surface energy to bewettable by fluid to be absorbed by the absorbent structure 101. Thiswettability is not required in all applications, however, and may beaccomplished using various surfactants known to those skilled in the artif the binder fiber is not intrinsically wettable.

Suitable binder fibers having a low melting temperature may be made frompolyethylene-polyvinyl alcohol (PE-PVA) block or random copolymers,polyethylene-polyethylene oxide (PE-PEO) block/graft copolymers,polypropylene-polyethylene oxide (PP-PEO) block/graft copolymers,polyester, polycaprolactone, polyamide, polyacrylates, polyurethane(ester or ether based). The melting point can be adjusted by adjustingthe content of VA or PEO (for those polymers with VA and PEO) or theconfiguration. The binder fiber material can be made by compounding witha twin extruder, Sigma mixer or other compounding equipment and thenmade into fibers by conventional non-woven processes like meltblowingand spunbonding.

As an example, absorbent structures incorporating such low meltingtemperature binder fibers are discussed in U.S. patent application Ser.No. 10/034,021, filed Dec. 20, 2002 and entitled Absorbent StructuresHaving Low Melting Fibers, the entire disclosure of which isincorporated herein by reference.

A number of other polymers and sensitizers may also, or mayalternatively, be used with the energy receptive additives in making thebinder fibers. Specifically selecting and/or positioning moieties alongthe polymer chain can affect the dielectric loss factor of the polymerand enhance the responsiveness of the polymer to electromagnetic energy.These include polymer composites from blend, block, graft, randomcopolymers, ionic polymers and copolymers and metal salts. Desirably,the presence of one or more moieties along the polymer chain causes oneor more of the following: (1) an increase in the dipole moments of thepolymer; and (2) an increase in the unbalanced charges of the polymermolecular structure. Suitable moieties include, but are not limited to,aldehyde, ester, carboxylic acid, sulfonamide and thiocyanate groups.

The selected moieties may be covalently bonded or ionically attached tothe polymer chain. As discussed above, moieties containing functionalgroups having high dipole moments are desired along the polymer chain.Suitable moieties include, but are not limited to, urea, sulfone, amide,nitro, nitrile, isocyanate, alcohol, glycol and ketone groups. Othersuitable moieties include moieties containing ionic groups including,but not limited to, sodium, zinc, and potassium ions.

For example, a nitro group may be attached to an aryl group within thepolymer chain. It should be noted that the nitro group may be attachedat the meta or para position of the aryl group. Further, it should benoted that other groups may be attached at the meta or para position ofthe aryl group in place of the nitro group. Suitable groups include, butare not limited to, nitrile groups. In addition to these modifications,one could incorporate other monomer units into the polymer to furtherenhance the responsiveness of the resulting polymer. For example,monomer units containing urea and/or amide groups may be incorporatedinto the polymer.

Suitable moieties include aldehyde, ester, carboxylic acid, sulfonamideand thiocyanate groups. However, other groups having or enhancingunbalanced charges in a molecular structure can also be useful; or amoiety having an ionic or conductive group such as, e.g., sodium, zinc,and potassium ions. Other ionic or conductive groups may also be used.

Specific combinations include low densityPE/polyethylene-polyvinylacetate block copolymer, LDPE/polyethyleneglycol, PE/polyacrylates, polyethylene-vinyl acetate copolymer,polyester, polyurethane, polyacrylates, polyethylene glycol (PEG),polyacrylamide (PAA), polyethylenimine (PEEM), polyvinyl acetate (PVAC),polyvinyl alcohol (PVA), polymethylacylic acid-sodium salt (PMA-Na),polyacylic acid sodium salt (PA-Na), and poly(styrenesolfonate-co-methyl acylic acid) sodium salt (P(SS-co-MA)-Na), andpolymers of terephthalic acid, adipic acid and 1,4 butanediol, andpolybutylene succinate copolymers. Other materials include polymers ofterephtalic acid, adipic acid and 1,4-butanediol, sold by BASFCorporation under the name ECOFLEX® or by Eastman Chemical Co. under thename Eastar Bio™ copolyester. Blends and grafted copolymers of the abovelisted polymers are also suitable.

Although various versions of the present invention are primarilydescribed herein as incorporating “binder fibers”, one of skill in theart will readily appreciate that other binder materials may be utilizedin the formation of the stabilized absorbent structure described herein.The term “binder material” as used herein is intended to include binderfibers and other materials which are activatable—as described herein—toform inter-fiber bonds within the absorbent structure for stabilizingthe absorbent structure. Consequently, the absorbent structures of thepresent invention may also include a quantity of binder material suchthat it can be provided as a stabilized absorbent structure. The bindermaterial can be of a polymeric or non-polymeric binder material that iscapable of forming ionic bonds, covalent bonds, or physical entanglementwith the fiber and/or the high absorbency material. Moreover, the bindermaterial may be a liquid or non-liquid binder material.

Examples of suitable polymeric binders can include polypropylene glycol(PPG); polyethylene glycol (PEG); polyacrylic acid (PAA);poly(caprolactone) diol; polyamide; cationic acrylamide copolymers;polyamine; polyamide-polyamine-epichlorohydrin (KYMENE); cationicamine-epichlorohydrin wet-strength agents; polyethylene imine agents;polyamide-epichlorohydrin agents with cellulose ethers or cationicstarches for improving paper wet-strength; polyacrylamides-glyoxal(e.g., PAREZ); urea-formaldehyde agents (UF); cationic modifiedureaformalin agents; melamine-formaldehyde agents (MF); cationicmodified melamine-formalin agents; polyethyleneimine (PEI); dialdehydestarch (DAS); proteinaceous adhesives treated with formaldehyde;cellulose xanthate (viscose); synthetic latexes; vegetable gums such asguar and bean gum; neutral (or alkaline-curing) thermosettingwet-strength agents; water-soluble polymers containing carboxyl groupsor carboxylate ions as their alkali metal or ammonium salts;substantially non-thermosetting tertiary-amino polyamide-epichlorohydrinagents.

Some commercial liquid binders are KYMENE 557LX, a polyamidoaminemodified with epichlorohydrin (available from Hercules); CREPEPLUS 75,97, a polyamidoamine modified with low epichlorohydrin content(available from Betz Paper Chemicals); CREPETROL 190, a polyamidoaminemodified with low epichlorohydrin content (available from Hercules);PEI, polyethylenimine, molecular weight 50,000-60,000, 50% (wt.) anaqueous liquid (available from Aldrich Chemical Co.); PEI-E apolyethylenimine modified with epichlorohydrin, base polymer mol. wt.20,000, 17% (wt) an aqueous liquid (available from Aldrich ChemicalCo.); POLYMIN PR971L, a high charge density, high molecular weightpolyethylenimine (available from BASF); POLYMIN SNA, a modified highmolecular weight polyethylenimine (available from BASF); and AGEFLOCWT-20VHV, a polydimethyldiallylammonium chloride (available from CPSChemical).

Examples of non-polymeric binders can include glycerin; ascorbic acid;urea; glycine; pentaerythritol; a monosaccharide or a disaccharide;citric acid; glyoxal; tartaric acid; dipropylene glycol; and ureaderivatives such as DMDHEU (dimethyldihydroxyethylurea). Suitablesaccharides can include glucose, sucrose, lactose, ribose, fructose,mannose, arabinose, and erythrose.

Stabilization of the absorbent structure may also be achieved by use ofemulsion binders. Physical strength can also be imparted by the use of aclass of materials described herein as “latex binders.” Examples of suchlatex binders include, but are not limited to, emulsion polymers such asthermoplastic vinyl acetate, C1-C8 alkyl ester of acrylic, methacrylicacid based adhesive, and combinations thereof. In particular, theemulsion polymerized thermoplastic adhesive can have a Tg from −25 to20° C., a solids content of from 45 to 60% by weight, typically from 52to 57%, and a Brookfield viscosity (#4 spindle, 60 rpm at 20° C.) offrom 5 to 1000 centipoises (cps). Suitable adhesives are vinylacetate/ethylene based adhesives incorporating less than about 10% anddesirably less than 5% by weight, of a polymerized third monomer.Representative examples of third monomers which may be incorporated intothe polymer include adhesion promoting monomers such as unsaturatedcarboxylic acid including acrylic and methacrylic acid, crotonic acid,and epoxide containing monomers such as glycidyl acrylate,glycidylmethacrylate and the like. The Airflex 401, 405 and 410 are someexamples. These binders can be obtained from Air Products and ChemicalsInc. located in Allentown, Pa., U.S.A. In addition, cross linkablebinders (thermoset) may be used to impart further wet strength thereto.The thermoset vinyl acetate/ethylene binders, such as vinylacetate/ethylene having from 1-3% N-methylolacrylamide such as Airflex124, 108 or 192, available from Air Products and Chemicals Inc., orElite 22 and Elite 33, available from National Starch & Chemicals,located in Bridgeport, N.J., U.S.A, are examples of suitable adhesivebinders.

To obtain a stabilization structure, emulsion polymerized thermoplasticpolymeric adhesive may be applied to an un-stabilizedfluff/superabsorbent structure in an amount ranging from 1 to 20 gramsdry adhesive per square meter of substrate. In particular aspects, 5 to15 grams of dry adhesive per square meter of substrate where the dryadhesive is applied by a spray method may provide suitable bonds.

Non-liquid binder material may also be used as a stabilizing agent. Forexample, binder powders may be used to stabilize absorbent structures.Binder powders for use in absorbent structures are available under thetrade name VINNEX available from Wacker Polymer Systems L.P., havingoffices in Adrian, Mich., U.S.A. Alternatively, thermally activatedbinder material, such as thermally activated binder fiber material, maybe used to stabilize absorbent structures. Binder fibers are typicallyused in airlaid absorbent structures for higher basis weight absorbentstructures, that is, greater than 120 gsm. Binder fibers generally havetwo components and are therefore termed bi-component fibers.Specifically, as representatively illustrated in FIG. 4, the twocomponents include a sheath 76 and a core 78. Other suitable binderfiber configurations also include side by side, islands in the sea, andthermoplastic staple fibers. Suitable binder fibers for use in absorbentstructures are available from KoSa, having offices in Houston, Tex.,U.S.A., Chisso Corporation, having offices in Tokyo, Japan, and TreviraGmbH, having offices in Bobingen, Germany.

The absorbent structure 101 of the present invention is desirably ofunitary construction. As used herein, the unitary construction of theabsorbent structure 101 is intended to refer to configurations whereinthe absorbent structure is a single non-woven web or layer comprising(i) a mixture of absorbent fibers, binder fibers and, optionally,superabsorbent material or (ii) absorbent fibers and, optionally,superabsorbent material. In the illustrated embodiment of FIGS. 1-4, asingle absorbent structure 101 comprises substantially the entireabsorbent body 53 of the diaper 21 (i.e., the dimensions of theabsorbent structure substantially define the dimensions of the absorbentbody). However, it is contemplated that the absorbent body 53 maycomprise more than one layer, wherein at least one of the layers is anabsorbent structure 101 of the present invention, and remain within thescope of this invention as long as the absorbent structure is itself ofunitary construction.

As an example, in one embodiment the absorbent structure 101 is made byfirst forming or otherwise collecting the absorbent fibers,superabsorbent material and binder fibers into a unitary structurehaving a desired shape, contour and/or material distribution prior toactivation of the binder fibers (e.g., prior to inter-fiber bondingwithin the absorbent structure) to define a non-woven, generallypre-stabilized absorbent structure. The binder fibers are subsequentlyactivated to form inter-fiber bonds within absorbent structure tothereby stabilize the absorbent structure.

Optionally, a substantially hydrophilic tissue wrapsheet (notillustrated) may be employed to help maintain the integrity of theabsorbent structure 101, or the entire absorbent body 53. The tissuewrapsheet is typically placed about the absorbent structure or theabsorbent body over at least the two major facing surfaces thereof andis composed of an absorbent cellulosic material, such as creped waddingor a high wet-strength tissue. The tissue wrapsheet can also beconfigured to provide a wicking layer that helps to rapidly distributeliquid to the absorbent fibers within the absorbent body 53. Thewrapsheet material on one side of the absorbent body may be bonded tothe wrapsheet located on the opposite side of the fibrous mass toeffectively entrap the absorbent body.

In one embodiment, the material composition of the pre-stabilizedabsorbent structure 101 (e.g., prior to activation of the binder fibers)may be from about 0.1 to about 60 weight percent binder fiber, fromabout 0 to about 80 weight percent superabsorbent material, and fromabout 5 to about 98 weight percent absorbent fibers. More particularembodiments may have from about 2 to about 10 weight percent binderfiber, from about 30 to about 70 weight percent superabsorbent materialand from about 30 to about 70 weight percent absorbent fiber. In otherembodiments, the pre-stabilized absorbent structure may have from about0.1 to about 5 weight percent binder fiber.

In another embodiment, the pre-stabilized absorbent structure 101 caninclude an amount of binder fibers which is at least about 0.1 weightpercent with respect to the total weight of the absorbent structure. Theamount of binder fibers can alternatively be at least about 1 weightpercent, and can optionally be at least about 3 weight percent. In otheraspects, the amount of binder fibers can be up to a maximum of about 30weight percent, or more. The amount of binder fibers can alternativelybe up to about 20 weight percent, and can optionally be up to about 5weight percent.

The absorbent fibers, binder fibers and superabsorbent material aredesirably distributed within the absorbent structure generally acrossthe full width of the absorbent structure, along the full length thereofand throughout the thickness thereof. However, the concentration ofabsorbent fibers, binder fibers and/or superabsorbent material withinthe absorbent structure 101 may be non-uniform (i) across the width ofthe absorbent structure, (ii) along the length of the absorbentstructure, and/or (iii) along the thickness or z-direction 127 of theabsorbent structure. For example, a heavier concentration of absorbentfibers, binder fibers and/or superabsorbent material may be disposed indifferent strata (e.g., in the z-direction) or in different regions(e.g., along the length or across the width) of the absorbent structure.

It is also contemplated that one or more strata or regions of theabsorbent structure 101 may be devoid of binder fibers and/orsuperabsorbent material, as long as the absorbent structure is ofunitary construction and includes binder fibers in at least a portion ofthe structure. It is further contemplated that binder fibers constructedof different materials may be disposed in different strata or regions ofthe absorbent structure 101 without departing from the scope of thisinvention.

The average basis weight of the pre-stabilized absorbent structure 101is desirably in the range of about 30 to about 2500 grams/square meter(gsm), more desirably within the range of about 50 to about 2000 gsm,and even more desirably within the range of about 100 to about 1500 gsm.The pre-stabilized absorbent structure 101 can also be formed to have anon-uniform basis weight across its width or along its length, with oneor more high basis weight regions, and one or more low basis weightregions. In at least one high basis weight region, at least asignificant portion of the absorbent structure 101 can have a compositebasis weight which is at least about 700 gsm. The high basis weightregion can alternatively have a basis weight of at least about 750 gsm,and can optionally have a basis weight of at least about 800 gsm. Inother aspects, the high basis weight region of the absorbent structure101 can have a composite basis weight of up to about 2500 gsm or more.The high basis weight region can alternatively have a basis weight ofless than or equal to about 2000 gsm, and more particularly less than orequal to about 1500 gsm.

Additionally, in at least one low basis weight region, thepre-stabilized absorbent structure 101 can have a composite basis weightof at least about 50 gsm. The low basis weight region can alternativelyhave a basis weight of at least about 100 gsm, and can optionally have abasis weight of at least about 150 gsm. In another alternativeconfiguration, the low basis weight region of the absorbent structure101 can have a composite basis weight of up to about 700 gsm, or more.The low basis weight region can alternatively have a basis weight of upto about 600 gsm, and can optionally have a basis weight of up to about500 gsm.

In another aspect of the present invention, the absorbent structure 101formed prior to activation of the binder fibers may have a density whichis at least a minimum of about 0.01 g/cc as determined at a restrainingpressure of 1.38 KPa (0.2 psi). The density can alternatively be atleast about 0.02 g/cc, and can optionally be at least about 0.03 g/cc.In other aspects, the density may be up to a maximum of about 0.12 g/cc,or more. The density can alternatively be up to about 0.11 g/cc, and canoptionally be up to about 0.1 g/cc. In one embodiment, the density ofthe pre-stabilized absorbent structure is substantially uniformthroughout the absorbent structure. In another embodiment, the densityis non-uniform across the width of the absorbent structure and/or alongthe length of the absorbent structure.

As used throughout the present application, the term “non-uniform” asused in reference to a particular characteristic or feature of theabsorbent structure, is intended to mean that the characteristic orfeature is non-constant or otherwise varies within the absorbentstructure in accordance with a pre-determined non-uniformity, e.g., anintended non-uniformity that is greater than non-uniformities resultingfrom normal processing and tolerance variations inherent in makingabsorbent structures. The non-uniformity may be present as either agradual gradient or as a stepped gradient, such as where theconcentration, basis weight and/or density changes abruptly from onestrata or region to an adjacent strata or region within the absorbentstructure, and may occur repeatedly within the absorbent structure ormay be limited to a particular portion of the absorbent structure.

The pre-stabilized absorbent structure 101 may also be formed to have athickness which is non-uniform along the length of the absorbentstructure and/or across the width of the absorbent structure. Thethickness is the distance between the major faces the absorbentstructure, as determined in a local z-direction of the absorbentstructure directed perpendicular to the planes of the major facesthereof at the location at which the thickness is determined. Avariation in thickness may be present as a gradual or otherwise slopedchange in thickness or as a stepped change in thickness whereby thethickness changes abruptly from one portion of the absorbent structureto an adjacent portion.

Accordingly, one or more portions of the absorbent structure 101 canhave a relatively lower thickness, and other portions of the absorbentstructure can have a relatively higher thickness. For example, in theillustrated embodiment, a portion 103 (FIGS. 2 and 4) of the absorbentstructure 101 which forms the absorbent body 53 of the diaper 21 issubstantially thicker than the rest of the absorbent structure andcorresponds generally to the front region 25 of the diaper to provide atargeted area of increased absorption capacity. The thicker portion 103of the absorbent structure 101 extends lengthwise less than the fulllength of the absorbent structure and is spaced longitudinally inward ofthe longitudinal ends of the structure. As shown in FIG. 2 the thickerportion 103 is also centrally positioned between the side edges 105 ofthe absorbent structure and spaced laterally inward from the side edgesthereof.

Additionally, or alternatively, the pre-stabilized absorbent structure101 may be formed to have a non-uniform width along the length of theabsorbent structure. The width is the distance between the side edges ofthe absorbent structure, as determined in a direction parallel to theY-axis of the absorbent structure. A variation in width may be presentas a gradual or otherwise sloped change in width or as a stepped changein which the width changes abruptly from one portion of the absorbentstructure to an adjacent portion. As an example, the absorbent structure101 may have any of a number of shapes, including rectangular, I-shaped,or T-shaped and is desirably narrower in the crotch region 27 than inthe front or back regions 25, 29 of the diaper 21. As illustrated inphantom in FIG. 1, the shape of the absorbent body 53 is defined by theabsorbent structure 101 and is generally T-shaped, with the laterallyextending crossbar of the “T” generally corresponding to the frontregion 25 of the diaper 21 for improved performance, especially for maleinfants.

It is understood, however, that the pre-stabilized absorbent structure101 may have a substantially uniform thickness and/or may have asubstantially uniform width, i.e., the side edges 105 of the absorbentstructure are substantially straight and in generally parallelrelationship with each other along the length of the absorbentstructure.

The absorbent structure 101 is formed in accordance with a desiredmethod for making such an absorbent structure whereby the absorbentfibers, superabsorbent material and binder fibers are collected on aforming surface while the binder fibers are in a pre-activatedcondition. The absorbent structure 101 is thus formed as a unitarystructure having a desired shape and contour (e.g., a desired length,width and/or thickness profile) before activation of the binder fibersoccurs, i.e., before inter-fiber bonding occurs within the absorbentstructure. The distribution of fibers and superabsorbent material withinthe pre-stabilized absorbent structure 101 may also be controlled duringformation thereof so that the concentration of materials, basis weightand/or density is substantially non-uniform prior to activation of thebinder fibers. The orientation of the absorbent fibers and binder fiberswithin the absorbent structure is desirably generally random followingformation of the pre-stabilized absorbent structure, including at themajor faces, side edges and longitudinal ends of the absorbentstructure.

The binder fibers are then activated to form inter-fiber bonds with theabsorbent fibers, the superabsorbent material (if present) and/or otherbinder fibers to stabilize the absorbent structure 101. Moreparticularly, in one embodiment the pre-stabilized absorbent structure101 is exposed to high-frequency electromagnetic energy (e.g., microwaveradiation, radio frequency radiation, etc.) to melt the binder fibersfor inter-fiber bonding with the absorbent fibers, and then cooled togenerally solidify the binder fibers to thereby secure the inter-fiberbonds between the binder fibers and the absorbent fibers.

The absorbent structure desirably remains unmolded during and afteractivation of the binder fibers. As used herein, the term unmoldedduring and after activation of the binder fibers means that the binderfibers are not subjected to an operation in which the shape and/ororientation thereof within the absorbent structure, and particularly atthe major faces, side edges and longitudinal ends of the absorbentstructure, is changed as a result of pressure being applied to thebinder fibers while the binder fibers are heated to a generally moltenor otherwise activated state. For example, in typical moldingoperations, the absorbent structure or at least one or both major facesof the absorbent structure is pressed against or within a mold during orafter heating of the binder fibers, or the mold itself may be heated soas to heat the binder fibers. Such a molding process forces areorientation of the absorbent structure fibers to a generallynon-random orientation and, and may also re-shape or even emboss themajor surfaces of the absorbent structure. Because the absorbentstructure 101 remains unmolded during and after activation of the binderfibers, the orientation of fibers within the absorbent structure,including at the major faces, side edges and longitudinal ends thereof,remains generally random during and after activation of the binderfibers to stabilize the absorbent structure.

Following stabilization of the absorbent structure 101, the structuremay have substantially the same shape, contour, material distributionand other characteristics as the pre-stabilized absorbent structure. Thestabilized absorbent structure 101 is desirably sufficiently strong tosupport a peak tensile load which is at least a minimum of about 100grams per inch (g/inch) of cross-directional (Y-axis) width of theabsorbent structure. The stabilized absorbent structure 101 strength canalternatively be at least about 200 g/inch, and can optionally be atleast about 500 g/inch. In other aspects, the absorbent structure 101strength can be up to a maximum of about 10000 g/inch, or more. Thestrength can alternatively be up to about 5000 g/inch, and canoptionally be up to about 2000 g/inch. In determining the strength ofthe stabilized absorbent structure 101, any previously formed,separately provided reinforcing component should be excluded from thedetermination. Such reinforcing components (not shown) may, for example,be provided by a scrim, a continuous filament fiber, a yarn, an elasticfilament, a tissue, a woven fabric, a non-woven fabric, an elastic film,a polymer film, a reinforcing substrate, or the like, as well ascombinations thereof.

The stabilized absorbent structure 101 can be configured to have astrength sufficient to support a peak tensile load which issignificantly greater than the peak tensile load that can be supportedby the absorbent structure prior to activation of the binder fibers. Ina particular aspect, the absorbent structure 101 can be configured tohave sufficient strength to support a peak tensile load which is atleast about 100% greater than the peak tensile load that can besupported by the absorbent structure prior to activation of the binderfibers. The stabilized structure 101 can alternatively be configured tosupport a peak tensile load which is at least about 200% greater.Optionally, the stabilized structure 101 can be configured to support apeak tensile load which is at least about 300% greater. The percentageof increase in the supported peak-load can be determined by the formula:100*(F2-F1)/F1;

-   -   where:    -   F1=the peak tensile load that can be supported by the absorbent        structure 101 prior to activation of the binder fibers; and    -   F2=the peak tensile load that can be supported by the stabilized        absorbent structure.

The peak load that can be supported by an absorbent structure 101 can bedetermined by employing TAPPI Test Method Number T 494 om-96 entitled“Tensile Properties of Paper and Paperboard” (using constant rate ofelongation apparatus) dated 1996. The test sample has a width of 1 inch(2.54 cm), and a length of 6 inches (15.24 cm). The jaws used wereINSTRON part number 2712-001 (available from Sintech, Inc., a businesshaving offices in Research Triangle Park, N.C., U.S.A.), and werearranged with an initial separation distance of 5 inches (12.7 cm). Thecross-head speed was 12.7 mm/min, and the testing employed a MTS SystemsCorp. model RT/1 testing machine controlled by TESTWORKS version 4.0software, which are available from MTS Systems Corp., a business havingoffice in Eden Prairie, Minn., USA. Substantially equivalent equipmentmay optionally be employed.

The fluid permeability of the absorbent structure 101 is also affectedby the incorporation of binder fibers therein to stabilize the absorbentstructure. The fluid permeability is defined by Darcy's Law and ismeasured for an absorbent saturated with a particular amount of fluid.More particularly, the permeability as that term is used herein isdetermined by the following permeability test.

In general, the higher the permeability of the absorbent structure whensaturated, the more open the structure is. As a result, the absorbentstructure can more easily take in additional fluid and is therefore lesslikely to leak. Without binder material, the permeability of a non-wovenabsorbent structure is based solely on the characteristics of theabsorbent fibers and superabsorbent material, if present, and thereforehas a relatively low fluid permeability, such as less than 20 squaremicrons. The integrity of the absorbent structure 101, and moreparticularly the void volume thereof, is increased by stabilizing thestructure with binder materials, and more particularly bymulti-component binder fibers, to substantially increase thepermeability of the absorbent structure. For example, followingactivation of the binder fibers, the stabilized absorbent structure 101desirably has a permeability throughout the absorbent structure asmeasured by the above permeability test of greater than 20 squaremicrons, more desirably greater than about 40 square microns, and evenmore desirably greater than about 60 square microns.

It is understood that the permeability may be non-uniform along at leastone of the length and the width of the absorbent structure 101, as longas the local permeability of the absorbent structure is at least greaterthan 20 square microns. Without being bound to theory, it is alsobelieved that an over-concentration of binder fibers within thestabilized absorbent structure can negatively affect the permeability ofthe absorbent structure. To facilitate increased permeability of theabsorbent structure, the binder fiber concentration within the absorbentstructure is desirably in the range of about 0.1 to about 10 percent,and more desirably in the range of about 0.1 to about 5 percent, tofacilitate increased permeability of the absorbent structure.

Where the binder fibers are activated by subjecting the pre-stabilizedabsorbent structure 101 to dielectric heating (e.g., by exposure toelectromagnetic energy), the stabilized absorbent structure also hasunique physical characteristics associated with the presence of thebinder fibers and subsequent activation by electromagnetic energy. Thesecharacteristics may be qualified and quantified using measurements oflocation and degree of oxidation and bonding efficiency within theabsorbent structure. More particularly, techniques such as ultraviolet,visible, near infrared, infrared and Raman spectroscopy; surfaceanalysis; differential scanning calorimetry; chromatographic separation;and various microscopic techniques can demonstrate the unique propertiesof materials heated “externally” via convection or infrared radiant heattransfer, versus “internally” using dielectric techniques.

With infrared and convection heating, radiant energy is translated intoheat at the outer surface of the absorbent structure where the surfacetemperature rises rapidly. Heat at the outer surface of the absorbentstructure eventually diffuses via thermal conduction toward the centerof the absorbent structure. This heating process is relatively slow andit takes a relatively significant time for the center of the absorbentstructure to reach the threshold temperature necessary to melt binderfibers disposed toward the center of the structure. The slow process ofthermal conduction is dependent upon the thermal conductivity of thestructure and its overall dimensions (e.g., thickness). For such aheating process, a greater oxidation of fibers consequently occurstoward, and more particularly on, the outer surface of the structure.Thermal bonding in this manner also results in some yellowing of thefibers at the outer surface of the absorbent structure.

For dielectric heating (e.g., using electromagnetic energy), the peaktemperature of the absorbent structure 101 is also near the outersurface. However, the temperature rise at the center of the absorbentstructure 101 is nearly identical to that at the outer surface. Thisoccurs since the dielectric heating process is active and direct. Thisdirect transfer of energy to the center of the absorbent structure isless dependent upon thermal conductivity and more dependent upon thedielectric field strength and dielectric properties of the absorbentstructure materials. In other words, the heating occurs generally fromthe center of the absorbent structure 101 out toward the outer surfacethereof.

Infrared energy must be applied from about 3 to 30 times longer thandielectric heating to achieve generally uniform heating throughout theabsorbent structure. More particularly, such an extended heating time isrequired in order to attain a desired temperature threshold (e.g., themelting temperature of the binder fiber) at the center of the absorbentstructure. When properly applied, dielectric heating occurs rapidly andmore uniformly. The rapid and uniform direct heating preventslarge-scale thermal degradation of polymers within the heated absorbentstructure.

FIGS. 5-10 illustrate one embodiment of an apparatus, generallyindicated at 121, for making an absorbent structure in accordance withthe present invention and the above-described method. The apparatus 121has an appointed lengthwise or machine-direction 123, an appointedwidthwise or cross-direction 125 which extends transverse to the machinedirection, and an appointed thickness or z-direction 127. For thepurposes of the present disclosure, the machine-direction 123 is thedirection along which a particular component or material is transportedlengthwise or longitudinally along and through a particular, localposition of the apparatus. The cross-direction 125 lies generally withinthe plane of the material being transported through the process, and isaligned perpendicular to the local machine-direction 123. Thez-direction 127 is aligned substantially perpendicular to both themachine-direction 123 and the cross-direction 125, and extends generallyalong a depth-wise, thickness dimension. In the illustrated embodiment,the machine direction 123 corresponds to the longitudinal X-axis of thediaper 21 of FIG. 1 and the cross-direction 125 corresponds to thelateral Y-axis of the diaper.

The apparatus 121 comprises an airforming device, generally indicated at131 in FIGS. 5 and 6, having a movable, foraminous forming surface 135extending about the circumference of a drum 137 (the reference numeralsdesignating their subjects generally). The drum 137 is mounted on ashaft 139 (FIG. 7) connected by bearings 141 to a support 143. As shownin FIG. 7, the drum includes a circular wall 145 connected to the shaft139 for conjoint rotation therewith. The shaft 139 is rotatably drivenby a suitable motor or line shaft (not shown) in a counter-clockwisedirection in the illustrated embodiment of FIGS. 5 and 6. The circularwall 145 cantilevers the forming surface 135 and the opposite side ofthe drum 137 is open. A vacuum duct 147 located radially inward of theforming surface 135 extends over an arc of the drum interior. The vacuumduct 147 has an arcuate, elongate entrance opening 149 under theforaminous forming surface 135, as will be described in more detailhereinafter, for fluid communication between the vacuum duct and theforming surface. The vacuum duct 147 is mounted on and in fluidcommunication with a vacuum conduit 151 connected to a vacuum source 153(represented diagrammatically in FIG. 7). The vacuum source 153 may be,for example, an exhaust fan.

The vacuum duct 147 is connected to the vacuum supply conduit 151 alongan outer peripheral surface of the conduit and extends circumferentiallyof the conduit. The vacuum duct 147 projects radially out from thevacuum conduit 151 toward the forming surface 135 and includes laterallyspaced side walls 147A and angularly spaced end walls 147B. The shaft139 extends through the wall 145 and into the vacuum supply conduit 151where it is received in a bearing 155 within the conduit. The bearing155 is sealed with the vacuum supply conduit 151 so that air is notdrawn in around the shaft 139 where it enters the conduit. The brace 157and entire conduit 21 are supported by an overhead mount 159.

A drum rim 161 (FIG. 7) is mounted on the wall 145 of the drum 137 andhas a multiplicity of holes over its surface area to provide asubstantially free movement of fluid, such as air, through the thicknessof the rim. The rim 161 is generally tubular in shape and extends aroundthe axis of rotation of the shaft 139 near the periphery of the wall145. The rim 161 is cantilevered away from the drum wall 145 and has aradially inward-facing surface positioned closely adjacent to theentrance opening 149 of the vacuum duct 147. To provide an air resistantseal between the rim 161 and the entrance opening 149 of the vacuum duct147, rim seals 163 are mounted on the inward-facing surface of the rim161 for sliding, sealing engagement with the walls 147A of the vacuumduct. Seals (not shown) are also mounted on the end walls 147B of thevacuum duct 147 for sliding, sealing engagement with the inward-facingsurface of the rim 161. The seals may be formed of a suitable materialsuch as felt to permit the sliding, sealing engagements.

Referring back to FIG. 6, the apparatus 121 further comprises a formingchamber 171 through which the forming surface 135 is movable conjointlywith the drum 137 upon rotation thereof. More particularly, in theillustrated embodiment the forming surface 135 moves in acounter-clockwise direction within the forming chamber 171 generallyfrom an entrance 173 through which the forming surface enters theforming chamber substantially free of fibrous material, and an exit 175through which the forming surface exits the forming chamber with thepre-stabilized absorbent structure 101 formed thereon. Alternatively,the drum 137 may rotate in a clockwise direction relative to the formingchamber 171. The forming chamber 171 is supported by a suitable supportframe (not shown) which may be anchored and/or joined to other suitablestructural components as necessary or desirable.

An absorbent fiber material, such as in the form of a batt 177 (FIGS. 5and 6) of absorbent fibers, is delivered from a suitable supply source(not shown) into a fiberizer 179, which may be a conventional rotaryhammer mill, a conventional rotatable picker roll or other suitablefiberizing device. The fiberizer 179 separates the batt 177 intodiscrete, loose absorbent fibers which are directed from the fiberizerinto the interior of the forming chamber 171. In the illustratedembodiment, the fiberizer 179 is disposed above the forming chamber 171.However, it is to be understood that the fiberizer 179 may instead belocated remote from the forming chamber 171 and that absorbent fibersmay be delivered to the interior of the forming chamber in other ways byother suitable devices and remain within the scope of the presentinvention.

Particles or fibers of superabsorbent material may be introduced intothe forming chamber 171 by employing conventional mechanisms such aspipes, channels, spreaders, nozzles and the like, as well ascombinations thereof. In the illustrated embodiment, superabsorbentmaterial is delivered into the forming chamber 171 via a deliveryconduit 181 and nozzle system (not shown). A binder fiber material isdelivered from a suitable binder fiber supply 183, such as in the formof bales (not shown), to a suitable opening device 185 to generallyseparate the binder fiber material into discrete, loose binder fibers.For example, the opening device 185 may be suitable for picking,carding, planing or the like, as well as combinations thereof.

Selected quantities of binder fiber are then directed to a meteringdevice 187, and the metering device feeds controlled quantities of thebinder fiber into a binder fiber delivery conduit 189. As an example,the binder fiber metering device 187 may be a model number CAM-1X12device which is available from Fiber Controls, Inc., a business havingoffices located in Gastonia, N.C., U.S.A. A blower 191 or other suitabledevice may be employed to help the flow of binder fibers through thedelivery conduit 189.

In the illustrated embodiment, the binder fiber conduit 189 delivers thebinder fibers into the fiberizer 171 for generally homogenous mixingwith the absorbent fibers such that a homogenous mixture of absorbentand binder fibers is subsequently delivered into the forming chamber171. However, it is understood that the binder fibers may instead bedelivered into the interior of the forming chamber 171 separate from theabsorbent fibers, and at a location other than at the delivery point atwhich the absorbent fibers are directed by the fiberizer 179 into theforming chamber.

Where the binder fibers are directed into the forming chamber 171 at alocation which is closer to the entrance 173 of the forming chamber, thebinder fibers will be more concentrated toward an inner or formingsurface side 193 (FIG. 6) or major face of the absorbent structure 101formed on the forming surface 135. Where the binder fibers are directedinto the forming chamber 171 at a location which is closer to the exit175 of the forming chamber, the binder fibers will be more concentratedtoward an outer or free-surface side 195 (FIG. 6) or major face of theabsorbent structure 101. As an alternative, the binder fibers may becombined with or otherwise incorporated into the source of the absorbentfibers instead of being separately delivered to the airforming device131. For instance, the binder fibers may be blended with the absorbentfibers before the absorbent fibers are formed into a supply roll (e.g.,the batt 177).

The foraminous forming surface 135 is defined in the illustratedembodiment by a series of mold elements, or form members 201 which arearranged end-to-end around the periphery of the forming drum 137 andindependently attached to the drum. As may be seen in FIG. 8, the formmembers 201 each define a substantially identical pattern in whichfibrous material is collected. The patterns correspond to a desiredlength, width and thickness of individual absorbent structures 101 whichrepeats over the circumference of the drum 137. However, partiallyrepeating or non-repeating pattern shapes may be used with the presentinvention. It is also understood that a continuous, un-patternedabsorbent structure may be formed on the forming surface 135, such aswhere the forming surface is flat or where the formed absorbentstructure is generally rectangular, and is subsequently processed (e.g.,cut or otherwise formed) to a desired shape.

With general reference now to FIGS. 8-10, the form members 201 comprisea foraminous member 205 which is operatively located on and secured tothe forming drum 135. The foraminous member 205 may include a screen, awire mesh, a hard-wire cloth, a perforated member or the like, as wellas combinations thereof. In the particular embodiment illustrated inFIG. 10, the foraminous member 205 is fluted to define open channels 209which extend generally radially to allow a substantially free flow ofair or other selected gas from the outer surface of the drum 137 towardthe interior of the drum. The channels 209 can have any desiredcross-sectional shape, such as circular, oval, hexagonal, pentagonal,other polygonal shape or the like, as well as combinations thereof.

With particular reference to FIG. 10, the radially outermost surfacedefined by the foraminous member 205 can be configured with anon-uniform depth-wise (e.g., z-direction 127) surface contour toprovide a desired non-uniform thickness of the pre-stabilized absorbentstructure 101 formed on the forming surface 135. In desiredarrangements, the z-direction 127 variation of the surface contour canhave a selected pattern which may be regular or irregular inconfiguration. For example, the pattern of the surface contour can beconfigured to substantially provide a selected repeat-pattern along thecircumferential dimension of the forming drum 137.

The surface contour of the foraminous member 205 shown in FIG. 10 thusdefines longitudinally opposite end regions having a first average depthand a central region having a second average depth that is greater thanthe first average depth. Each end region with the first average depthcan provide a lower-basis-weight region and/or thickness of theabsorbent structure 101 formed on the forming surface 135, and thecentral region with the greater second average depth can provide arelatively higher-basis-weight and/or thickness region of the absorbentstructure. Desirably, each region with the first average depth can besubstantially contiguous with an adjacent region with the greater seconddepth. It is also understood that the foraminous member 205 may beconfigured to have a z-direction 127 surface contour across the width ofthe forming surface 135 for providing a non-uniform basis weight and/orthickness across the width of the absorbent structure 101 formed on theforming surface.

In desired arrangements, the surface contour of the foraminous member205 defines a generally trapezoidal shape. Alternatively, the contourmay define a domed shape or may be flat. In the illustrated embodiment,the depth profile defined by the foraminous member 205 forms a pocketregion 211 extending in the machine direction 123 along a portion of thelength of the forming surface 135 and across a central portion of thewidth thereof for forming the absorbent structure illustrated in FIG. 4.

In a further aspect, one or more non-flow regions of the forming surfacemay be formed by employing a suitable blocking mechanism (not shown)which covers or otherwise occludes the flow of air through selectedregions of the forming surface 135. As a result, the blocking mechanismcan deflect or reduce the amount of fibers deposited on the areas of theforming surface 135 covered by the blocking mechanism. The blockingmechanism can optionally be configured to form other desired features ofthe absorbent structure 101, such as a series of key notches (not shown)on the formed absorbent structure. The key notches can, for example,provide a sensing point for locating and positioning a subsequentsevering of a web of longitudinally connected absorbent structures 101formed on the forming surface 135 into discrete absorbent structures.

Still referring to FIGS. 8-10, the form members 201 can also include oneor more side-masking members 213, also sometimes referred to as contourrings, configured to provide a desired shape (e.g., width profile) tothe absorbent structure 101. For example, in the illustrated embodimentthe side-masking members 213 are provided by a pair of laterally opposedring members which extend circumferentially around the forming drum 137in laterally (cross-direction 125) opposed relationship with each other.Each of the members 213 has a non-uniform inner side wall 215 along itsrespective length so that the laterally opposed inner side walls of theside-masking members 213 define the width profile of the absorbentstructure 101 formed on the forming surface 135. More particularly, theinner side walls 215 of the side-masking members 213 have a generallyserpentine contour as they extend in the machine direction 123. As aresult, the side-masking members 213 provide alternating narrower andwider regions of the form members 201. Accordingly, the absorbentstructure 101 delivered from the airforming device 131 can have a widthprofile which is non-uniform along at least a portion of the length ofthe structure.

In another feature, at least one of the side-masking members 213 caninclude one or more key tabs (not shown). The individual key tabs may,for example, be employed for marking or otherwise identifying eachintended absorbent structure 101 length along the circumference of theforming drum 137. Such side-masking members 213 can be particularlyadvantageous when the airforming device 131 is employed to produceabsorbent structures for use in disposable, shaped absorbent articles,such as diapers, children's training pants, feminine care products,adult incontinence products and the like.

It is understood that the inner side walls 215 of the side-maskingmembers 213 can instead be generally straight (e.g., parallel to themachine direction 123) to produce a substantially rectangular, ribbonshaped absorbent structure 101. It is also understood that the sideedges 105 of the absorbent structure 101 can alternatively be providedby cutting and removal, cutting and folding, or the like, as well ascombinations thereof.

While the forming surface 135 is illustrated herein as being part of theforming drum 137, it is to be understood that other techniques forproviding the forming surface 135 may also be employed without departingfrom the scope of the present invention. For example, the formingsurface 135 may be provided by an endless forming belt (not shown). Aforming belt of this type is illustrated in U.S. Pat. No. 5,466,409,entitled FORMING BELT FOR THREE-DIMENSIONAL FORMING APPLICATIONS by M.Partridge et al. which issued on Nov. 14, 1995.

In operation to make a formed, non-woven pre-stabilized absorbentstructure, e.g., prior to activation of the binder fibers to forminter-fiber bonds within the absorbent structure, the vacuum source 153(FIG. 7) creates a vacuum in the vacuum duct 147 relative to theinterior of the forming chamber 171. As the forming surface 135 entersand then moves through the forming chamber 171 toward the exit 175thereof, the absorbent fibers, binder fibers and superabsorbent materialwithin the forming chamber are operatively carried or transported by anentraining air stream and drawn inward by the vacuum toward theforaminous forming surface. It is understood that the absorbent fibers,superabsorbent materials and binder fibers may be entrained in anysuitable fluid medium within the forming chamber 171. Accordingly, anyreference herein to air as being the entraining medium should beunderstood to be a general reference which encompasses any otheroperative entraining fluid. Air passes inward through the formingsurface 135 and is subsequently passed out of the drum 137 through thevacuum supply conduit 151. Absorbent fibers, binder fibers and,optionally, superabsorbent materials are collected by the form members201 to thereby form the pre-stabilized absorbent structure 101.

It is understood that the level or strength of the vacuum suction can beselectively regulated to control the density of the absorbent structure101 formed on the forming surface 135. A relatively greater suctionstrength can be employed to produce a relatively higher density, or lowporosity, in the absorbent structure 101, and a relatively lower suctionstrength can be employed to produce a relatively lower density, or highporosity, in the absorbent structure. The specific level of suctionstrength will depend upon the specific flow characteristics present inthe forming chamber 171. It is readily apparent that a desired suctionstrength can be found by employing a short, iterative series of wellknown trial steps. The density of the absorbent structure 101 prior toactivation of the binder fibers can be important for controlling thedesired functional properties of the subsequently stabilized absorbentstructure.

Subsequently, the drum 137 carrying the absorbent structure 101 passesout of the forming chamber 171 through the exit 175 to a scarfingsystem, generally indicated at 271 in FIGS. 5 and 6, where excessthickness of the absorbent structure can be trimmed and removed to apredetermined extent. The scarfing system 271 includes a scarfingchamber 273 and a scarfing roll 275 positioned within the scarfingchamber. The scarfing roll 275 abrades excess fibrous material from theabsorbent structure 101, and the removed materials are transported awayfrom the scarfing chamber 273 within a suitable discharge conduit as iswell known in the art. The removed fibrous material may, for example, berecycled back into the forming chamber 171 or the fiberizer 179, asdesired. Additionally, the scarfing roll 275 can rearrange andredistribute the fibrous material along the machine-direction 123 of theabsorbent structure 101 and/or along the lateral or cross-machinedirection 125 of the absorbent structure.

The rotatable scarfing roll 275 is operatively connected and joined to asuitable shaft member (not shown), and is driven by a suitable drivesystem (not shown). The drive system may include any conventionalapparatus, such as a dedicated motor, or a coupling, gear or othertransmission mechanism operatively connected to the motor or drivemechanism used to rotate the forming drum 137. The scarfing system 271can provide a conventional trimming mechanism for removing orredistributing any excess thickness of the absorbent structure 101 thathas been formed on the forming surface 135. The scarfing operation canyield an absorbent structure 101 having a selected contour on a majorface-surface thereof (e.g., the free surface side 193 in the illustratedembodiment) that has been contacted by the scarfing roll 275. Forexample, the scarfing roll 275 may be configured to provide asubstantially flat surface along the scarfed surface of the absorbentstructure 101, or may optionally be configured to provide a non-flatsurface. The scarfing roll 275 is disposed in spaced adjacentrelationship with the forming surface 135, and the forming surface istranslated past the scarfing roll upon rotation of the drum 137.

The scarfing roll 275 of the illustrated embodiment rotates in aclockwise direction which is counter to the direction of rotation of thedrum 137. Alternatively, the scarfing roll 275 may be rotated in thesame direction as the forming surface 135 on the forming drum 137. Ineither situation, the rotational speed of the scarfing roll 275 shouldbe suitably selected to provide an effective scarfing action against thecontacted surface of the formed absorbent structure 101. In like manner,any other suitable trimming mechanism may be employed in place of thescarfing system 271 to provide a cutting or abrading action to thefibrous absorbent structure 101 by a relative movement between theabsorbent structure and the selected trimming mechanism.

After the scarfing operation, the portion of the forming surface 135 onwhich the absorbent structure 101 is formed can be moved to a releasezone of the apparatus 121 disposed exterior of the forming chamber 171.In the release zone, the absorbent structure 101 is drawn away from theforming surface 135 onto a conveyor, which is indicated generally at 281in FIGS. 5 and 6. The release can be assisted by the application of airpressure from the interior of the drum 137. The conveyor 281 receivesthe formed absorbent structure 101 from the forming drum 137 and conveysthe absorbent structure to a collection area or to a location forfurther processing (not shown). Suitable conveyors can, for example,include conveyer belts, vacuum drums, transport rollers, electromagneticsuspension conveyors, fluid suspension conveyors or the like, as well ascombinations thereof.

In the illustrated embodiment, the conveyor 281 includes an endlessconveyor belt 283 disposed about rollers 285. A vacuum suction box 287is located below the conveyor belt 283 to draw the absorbent structure101 away from the forming surface 135. The belt 283 is perforate and thevacuum box 287 defines a plenum beneath the portion of the belt in closeproximity to the forming surface so that the vacuum within the vacuumbox acts on the absorbent structure 101 on the forming surface 135.Removal of the absorbent structure 101 from the forming surface 135 canalternatively be accomplished by the weight of the absorbent structure,by centrifugal force, by mechanical ejection, by positive air pressureor by some combination thereof or by another suitable method withoutdeparting from the scope of this invention. As an example, in theillustrated embodiment, the absorbent structures 101 exiting the formingchamber are interconnected end-to-end to form a web or series ofabsorbent structures, each of which has a selected shape thatsubstantially matches the shape provided by the corresponding formmembers 201 used to form each individual absorbent structure.

Referring now to FIG. 5, after the pre-stabilized absorbent structures101 are transferred from the forming surface 135 to the conveyor 281,each absorbent structure is subsequently transported to an activationsystem 304 wherein the binder fibers are activated to form inter-fiberbonds within the absorbent structure. In one embodiment, the binderactivation system 304 includes an activation chamber 306 through whicheach absorbent structure 101 passes, and a generator 308 for radiatingelectromagnetic energy within the activation chamber as each absorbentstructure passes therethrough. For example, a suitable microwavegenerator 308 can produce an operative amount of microwave energy, andcan direct the energy through a suitable wave-guide 310 to theactivation chamber 306.

In one embodiment, the electromagnetic energy may be radio frequency(RF) energy having an RF frequency which is at least a minimum of about0.3 megahertz (MHz). The frequency can alternatively be at least about300 MHz, and can optionally be at least about 850 MHz. In other aspects,the frequency can be up to a maximum of about 300000 MHz, or more. Thefrequency can alternatively be up to about 30000 MHz, and can optionallybe up to about 2600 MHz. In a particular embodiment, the radio frequencyis desirably about 27 MHz. In another embodiment, the electromagneticenergy may be microwave energy in the range of about 915 MHz to about2450 MHz.

In a particular arrangement, the electromagnetic energy can operativelyheat the binder fibers to a temperature above the melting point of thebinder fiber material. The melted binder fibers can then adhere orotherwise bond and operatively connect to the absorbent fibers, to thesuperabsorbent material and/or to other binder fibers within theabsorbent structure. The binder fibers may also be activatedsubstantially without heating up the entire mass of the absorbentstructure 101. In a particular feature, the binder fibers can be rapidlyactivated while substantially avoiding any excessive burning of theabsorbent structure 101.

The heating and melt activation of the binder fibers can be produced byany operative mechanism available in the absorbent structure 101. Forexample, the electromagnetic energy may heat water vapor present withinthe absorbent structure 101, and the heated vapor can operatively meltthe binder fibers. In another mechanism, the electromagnetic energy canbe absorbed by the binder fibers and the absorbed energy can operativelyheat and melt the binder fibers.

The total residence time of the absorbent structure 101 within theactivation chamber 306 can provide a distinctively efficient activationperiod. In a particular aspect, the activation period can be at least aminimum of about 0.002 sec. The activation period can alternatively beat least about 0.005 sec, and can optionally be at least about 0.01 sec.In other aspects, the activation period can be up to a maximum of about3 sec. The activation period can alternatively be up to about 2 sec, andcan optionally be up to about 1.5 sec.

The activation chamber 304 can be a tuned chamber within which theelectromagnetic energy can produce an operative standing wave. In aparticular feature, the activation chamber 304 can be configured to be aresonant chamber. Examples of suitable arrangements for the resonant,activation chamber system are described in a U.S. Pat. No. 5,536,921entitled SYSTEM FOR APPLYING MICROWAVE ENERGY IN SHEET-LIKE MATERIAL byHedrick et al. which has an issue date of Jul. 16, 1996; and in U.S.Pat. No. 5,916,203 entitled COMPOSITE MATERIAL WITH ELASTICIZED PORTIONSAND A METHOD OF MAKING THE SAME by Brandon et al. which has an issuedate of Jun. 29, 1999. The entire disclosures of these documents areincorporated herein by reference in a manner that is consistentherewith. Another suitable activation system for activating the binderfibers is disclosed in U.S. patent application Ser. No. 10/037,385,filed Dec. 20, 2001, and entitled Method and Apparatus for MakingOn-Line Stabilized Absorbent Materials.

The absorbent structure 101 exiting the activation chamber 304 can alsobe selectively cooled or otherwise processed following heating of thebinder fibers. The cooling of the absorbent structure 101 may beprovided by a cooling system that includes: chilled air, a refrigeratedatmosphere, radiant cooling, transvector cooling, ambient air cooling,or the like, as well as combinations thereof. As representatively shownin FIG. 5, the cooling system may include a chilled-air supply hood 321,a vacuum conveyor 323, a blower 325 and a chiller or other refrigerationunit 327. The refrigeration unit 327 can provide a suitable coolant to aheat exchanger 329, and the blower can circulate air through the heatexchanger for cooling. The cooled air can be directed into the supplyhood 321 and onto the absorbent structure 101. The air can then be drawnout of the hood 321 for recirculation through the heat exchanger 329.

In a particular aspect, the absorbent structure 101 can be cooled to asetting temperature which is below the melting temperature of the binderfiber material. In another aspect, the absorbent structure 101 can becooled to a temperature of not more than a maximum of 200° C. within aselected setting distance downstream of the activation chamber 304. In afurther feature, the absorbent structure 101 can be cooled to atemperature of not more than a maximum of 150° C. within the selectedsetting distance. Accordingly, the setting distance can be measuredafter ending the exposure of the absorbent structure 101 to thehigh-frequency electromagnetic energy in the activation chamber 304. Ina particular feature, the setting distance can be a minimum of about 0.5m. The setting distance can alternatively be at least a minimum of about0.75 m, and can optionally be at least about 1 m. In another feature,the setting distance can be a maximum of not more than about 30 m. Thesetting distance can alternatively be not more than about 20 m, and canoptionally be not more than about 10 m.

In another aspect, an incremental portion of the heated absorbentstructure 101 may be cooled to the desired setting temperature within adistinctive setting period, as determined from the time that theincremental portion of the activated structure exits the activationchamber 304. Accordingly, the setting period can be measured afterending the exposure of the absorbent structure to the high-frequencyelectromagnetic energy in the activation chamber 304. In a particularfeature, the setting period can be a minimum of about 0.05 sec. Thesetting period can alternatively be at least a minimum of about 0.075sec., and can optionally be at least about 0.1 sec. In another feature,the setting period can be a maximum of not more than about 3 sec. Thesetting period can alternatively be not more than about 2 sec., and canoptionally be not more than about 1 sec.

The temperature of the absorbent structure 101 can be determined byemploying an infrared scanner, such as a Model No. LS601RC60, availablefrom Land Infrared, a business having offices located in Bristol, Pa.,U.S.A. With this device, the temperature can be determined by aiming themeasurement probe at the centerline of the structure 101, and setting upthe probe (in accordance with the instruction manual) at a separationdistance of 12 inches, as measured perpendicular to the structure.Alternatively, a substantially equivalent device may be employed.

The stabilized absorbent structure 101 may also be compressed (e.g., bysubjecting the structure to a debulking operation) to provide a desiredthickness and density to the stabilized absorbent structure. In adesired aspect, the debulking is conducted after the absorbent structurehas been cooled. As representatively shown, the debulking operation canbe provided by a pair of counter-rotating nip rollers 331. The debulkingoperation can alternatively be provided by a converging conveyor system,indexed platens, elliptical rollers, or the like, as well ascombinations thereof.

In a particular aspect, the thickness of the absorbent structurefollowing debulking can be a minimum of about 0.5 mm. The debulkedthickness can alternatively be at least about 1 mm, and can optionallybe at least about 2 mm. In another aspect, the debulked thickness can beup to a maximum of about 25 mm. The debulked thickness can alternativelybe up to about 15 mm, and can optionally be up to about 10 mm.

In another aspect, the debulked stabilized absorbent structure 101 canhave a density which is at least a minimum of about 0.05 g/cm³. Thedebulked density can alternatively be at least about 0.08 g/cm³, and canoptionally be at least about 0.1 g/cm³. In further aspects, the debulkeddensity can be up to a maximum of about 0.5 g/cm³, or more. The debulkeddensity can alternatively be up to about 0.45 g/cm³, and can optionallybe up to about 0.4 g/cm³.

In optional configurations, the stabilized absorbent structure 101 maybe cut or otherwise divided to provide a desired lateral shaping (e.g.,width profile) of the structure, and/or to provide a laterally contouredstructure. The cutting system may, for example, include a die cutter, awater cutter, rotary knives, reciprocating knives or the like, as wellas combinations thereof. The shaping may be conducted prior to and/orafter the absorbent structure 101 is subjected to the activation of thebinder fiber with the selected activation system 304.

Stabilized absorbent structures such as those described herein performquite well for their intended purposes. While conducting research intovarious aspects of stabilized absorbent structures, the presentinventors discovered that the flexibility of stabilized absorbentstructures can be enhanced by introducing discontinuous absorbent zonesinto at least a portion of the absorbent structure. Referring now to theabsorbent structure 101 illustrated in FIGS. 11 and 12, thesediscontinuous absorbent zones 404 define one or more channels 400 thatmay run in a longitudinal length direction and/or a transverse widthdirection. Moreover, the present inventors discovered that theflexibility of non-stabilized absorbent structures (i.e., thoseabsorbent structure that have not been stabilized and/or those absorbentstructures that are free of binder fiber) can also be enhanced byintroducing discontinuous absorbent zones into at least a portion of theabsorbent structure. Consequently, one of skill in the art willappreciate that many aspects disclosed herein as relating to stabilizedabsorbent structures are also applicable to non-stabilized absorbentstructures.

The channels 400 are introduced into the absorbent structure 101 byinserting a forming member 402 into a foraminous member similar toforaminous member 205. Suitably, the forming member 402 is of sufficientdesign to allow for the formation of an absorbent structure 101, atleast a portion of the absorbent structure so formed havingdiscontinuous absorbent zones 404 that define channels 400. While one ofskill in the art will readily appreciate upon reading this disclosurethat a number of configurations will be effective, one particularconfiguration provides for a forming member 402 similar to thatillustrated in FIG. 13. A suitable forming member 402 may be constructedof a variety of materials a long as the materials produce a formingmember having a relatively smooth surface or surfaces. A relativelysmooth surface allows the absorbent structure 101 to be separated fromthe forming member 402 without significantly disturbing the orientationof the fibers of the absorbent structure.

An absorbent structure 101 having discontinuous absorbent zones 404 maybe formed according to a variety of methods including in the followingmethod. Initially, a forming member 402 is inserted into a foraminousmember, such as foraminous member 205 illustrated in FIGS. 8 through 10.The depth (in the z direction) of the forming member 402 will depend onthe desired depth of any channel(s) 400. Once the forming member 402 isinserted, the fibers (and, optionally, the superabsorbent material) areintroduced into the foraminous member 205. After the fibers—and anyoptional superabsorbent material—are introduced and the absorbentstructure 101 having discontinuous absorbent zones 404 is formed, theabsorbent structure is removed from the foraminous member 205. Theabsorbent structure 101 so formed may be subjected to any of a number ofsteps prior to stabilization (if stabilization is desired) and tailoredto the intended use of the absorbent structure. In the event theabsorbent structure 101 is to be stabilized, it is thereafter subjectedto an appropriate method of stabilization as described herein. In analternative approach, the absorbent structure 101 may be stabilizedprior to removal of the forming member 402.

Desirably, the absorbent structures of the present invention have atleast one channel 400. Any channel 400 running in a longitudinal lengthdirection is typically spaced between the side edges 31 of the absorbentstructure 101. Any such longitudinally-extending channel or channels 400may be spaced equally or unequally between the side edges 31. Anychannel 400 running in a lateral width direction is typically spacedbetween the waist edges 33 and 35. Any such laterally-extending channelor channels may be spaced equally or unequally between the waist edges33 and 35.

Desirably any channel 400 extends through no less than 10;alternatively, no less than 15; alternatively, no less than 20;alternatively, no less than 25; alternatively, no less than 30;alternatively, no less than 35; alternatively, no less than 40;alternatively, no less than 45; alternatively, no less than 50;alternatively, no less than 55; alternatively, no less than 60;alternatively, no less than 65; alternatively, no less than 70;alternatively, no less than 75; alternatively, no less than 80; andfinally, alternatively, no less than 85 percent of the thickness of theabsorbent structure 101. In addition, any channel 400 desirably extendsthrough no more than 90; alternatively, no more than 85; alternatively,no more than 80; alternatively, no more than 75; alternatively, no morethan 70; alternatively, no more than 65; alternatively, no more than 60;alternatively, no more than 55; alternatively, no more than 50;alternatively, no more than 45; alternatively, no more than 40;alternatively, no more than 35; alternatively, no more than 30;alternatively, no more than 25; alternatively, no more than 20; andfinally, alternatively, no more than 15 percent of the thickness of theabsorbent structure 101. Thus, any channel 400 desirably extends throughthe thickness of the absorbent structure 101 in an amount rangingbetween no less than 10 up to no more than 90 percent; although theapproximate amount may vary according to, inter alia, the general designand intended use of the absorbent structure.

To enjoy many of the benefits of the present invention, any channel 400running in a longitudinal length direction desirably extends no morethan 100; alternatively, no more than 95; alternatively, no more than90; alternatively, no more than 85; alternatively, no more than 80;alternatively, no more than 75; alternatively, no more than 70; andfinally, alternatively, no more than 65 percent of the longitudinallength of the absorbent structure 101. In addition, any channel runningin a longitudinal length direction desirably extends no less than 20;alternatively, no less than 25; alternatively, no less than 30;alternatively, no less than 35; alternatively, no less than 40;alternatively, no less than 45; alternatively, no less than 50;alternatively, no more than 55; and finally, alternatively, no less than60 percent of the longitudinal length of the absorbent structure 101.Thus, any channel 400 running in a longitudinal length directiondesirably extends the longitudinal length of the absorbent structure 101in an amount ranging between no less than 20 up to no more than 100percent; although the approximate amount may vary according to, interalia, the general design and intended use of the absorbent structure.

In addition, any channel 400 running in a lateral width directionsuitably extends no more than 100; alternatively, no more than 95;alternatively, no more than 90; alternatively, no more than 85;alternatively, no more than 80; alternatively, no more than 75;alternatively, no more than 70; alternatively, no more than 65;alternatively, no more than 60; alternatively, no more than 55;alternatively, no more than 50; and finally, alternatively, no more than45 percent of the lateral width of the absorbent structure 101. Inaddition, any channel 400 running in a lateral width direction suitablyextends no less than 20; alternatively, no less than 25; alternatively,no less than 30; alternatively, no less than 35; alternatively, no lessthan 40; alternatively, no less than 45; alternatively, no less than 50;alternatively, no less than 55; alternatively, no less than 60;alternatively, no less than 65; alternatively, no less than 70;alternatively, no less than 75; and finally, alternatively, no less than80 percent of the lateral width of the absorbent structure 101. Thus,any channel 400 running in a lateral width direction suitably extendsthe lateral width of the absorbent structure 101 in an amount rangingbetween no less than 20 up to no more than 100 percent; although theapproximate amount may vary according to, inter alia, the general designand intended use of the absorbent structure.

The width (in the x-y planes, as opposed to thickness in the z plane) ofany channel 400 is such that the absorbent structure 101 demonstratesthe enhanced flexibility desired, but not so wide as to cause discomfortto the wearer of any disposable absorbent article incorporating theabsorbent structures of the present invention. Suitably, the width ofany channel 400 is no less than 0.4; alternatively, no less than 0.5;alternatively, no less than 0.6; alternatively, no less than 0.7;alternatively, no less than 0.8; alternatively, no less than 0.9;alternatively, no less than 1; alternatively, no less than 1.5;alternatively, no less than 2; alternatively, no less than 2.5;alternatively, no less than 3; alternatively, no less than 4;alternatively, no less than 5; alternatively, no less than 6;alternatively, no less than 7; alternatively, no less than 8;alternatively, no less than 9; alternatively, no less than 9.5;alternatively, no less than 10; alternatively, no less than 10.5;alternatively, no less than 11; and finally, alternatively, no less than11.5 mm. Suitably, the width of any channel 400 is no more than 12;alternatively, no more than 11; alternatively, no more than 10;alternatively, no more than 9; alternatively, no more than 8;alternatively, no more than 7; alternatively, no more than 6;alternatively, no more than 5; alternatively, no more than 4;alternatively, no more than 3; alternatively, no more than 2;alternatively, no more than 1; and finally, alternatively, no more than0.5 mm. Consequently, any channel 400 suitably has a width rangingbetween no less than 0.4 up to no more than 12 mm; although theapproximate width may vary according to, inter alia, the general designand intended use of the absorbent structure.

The various absorbent structures of the present invention alsodemonstrate an improved flexibility when compared to an otherwisesimilar absorbent structure free of any discontinuous absorbent zones. Astabilized absorbent structure having discontinuous absorbent zonesgenerally has a cylindrical compression at yield which is at least 55;alternatively, at least 60; alternatively, at least 65; alternatively,at least 70; alternatively, at least 75; and finally, alternatively, atleast 80 percent less than the cylindrical compression at yield of anotherwise similar stabilized absorbent structure free of any suchdiscontinuous zone(s). Moreover, a non-stabilized absorbent structurehaving discontinuous absorbent zones generally has a cylindricalcompression at yield which is at least 25; alternatively, at least 30;alternatively, at least 35; alternatively, at least 40; alternatively,at least 45; alternatively, at least 50; alternatively, at least 55;alternatively, at least 60; alternatively at least 65; alternatively, atleast 70; and finally, alternatively, at least 75 percent less than thecylindrical compression at yield of an otherwise similar non-stabilizedabsorbent structure free of any such discontinuous zone(s).

One version of the present invention provides for an absorbent bodysuitable for incorporation into a disposable absorbent article. Theabsorbent body includes a non-woven absorbent structure having a unitaryconstruction and absorbent fibers similar to those described herein.Optionally, the absorbent structure also includes superabsorbentmaterial. The absorbent structure 101 has a longitudinal length, alateral width and a thickness. At least a portion of the absorbentstructure 101 has discontinuous absorbent zones 404 that define at leasttwo channels 400. In this version, at least one of the channels 400 runsin a longitudinal length direction of the absorbent structure 101. Alsoin this version, at least one of the channels 400 runs in a lateralwidth direction of the absorbent structure 101. Interesting, the presentinventors also found that the density of the absorbent structure 101 inthe channels 400 is less than or equal to the density of a portion ofthe absorbent structure adjacent the channel(s). This version of theabsorbent structure 101 may either be non-stabilized or stabilized.

Another version of the present invention provides for an absorbentarticle comprising a fluid pervious liner, a liquid impervious outercover and an absorbent body. The absorbent body is disposed between theliner and the outer cover. The absorbent body includes a non-wovenabsorbent structure having a unitary construction and absorbent fiberssimilar to those described herein. Optionally, the absorbent structurealso includes superabsorbent material. The absorbent structure 101 has alongitudinal length, a lateral width and a thickness. At least a portionof the absorbent structure 101 has discontinuous absorbent zones 404that define at least two channels 400. In this version, at least one ofthe channels 400 runs in a longitudinal length direction of theabsorbent structure 101. Also in this version, at least one of thechannels 400 runs in a lateral width direction of the absorbentstructure 101. Interestingly, the present inventors also found that thedensity of the absorbent structure 101 in the channels 400 is less thanor equal to the density of a portion of the absorbent structure adjacentthe channel(s). This version of the absorbent structure 101 may eitherbe non-stabilized or stabilized.

Still another version of the present invention provides for an absorbentbody suitable for incorporation into a disposable absorbent article. Theabsorbent body includes a non-woven absorbent structure having a unitaryconstruction and absorbent fibers similar to those described herein.Optionally, the absorbent structure also includes superabsorbentmaterial. The absorbent structure 101 has a longitudinal length, alateral width and a thickness. At least a portion of the absorbentstructure 101 has discontinuous absorbent zones 404 that define at leastfour channels 400. In this version, at least two of the channels 400 runin a longitudinal length direction of the absorbent structure 101. Alsoin this version, at least two of the channels 400 run in a lateral widthdirection of the absorbent structure 101. Interestingly, the presentinventors also found that the density of the absorbent structure 101 inthe channels 400 is less than or equal to the density of a portion ofthe absorbent structure adjacent the channel(s). This version of theabsorbent structure 101 may either be non-stabilized or stabilized. Whennon-stabilized, that portion of the absorbent structure 101 having thediscontinuous absorbent zones 404 has a cylindrical compression at yieldwhich is at least 55 percent less than the cylindrical compression atyield of an otherwise similar absorbent structure free of thediscontinuous absorbent zones. When stabilized, that portion of theabsorbent structure 101 having the discontinuous absorbent zones 404 hasa cylindrical compression at yield which is at least 30 percent lessthan the cylindrical compression at yield of an otherwise similarabsorbent structure free of the discontinuous absorbent zones.

EXAMPLES

The following Examples describe various versions of the invention. Otherversions within the scope of the claims herein will be apparent to oneskilled in the art from consideration of the specification or practiceof the invention as disclosed herein. It is intended that thespecification, together with the Examples, be considered exemplary only,with the scope and spirit of the invention being indicated by the claimswhich follow the Examples.

Example 1

In this Example, a non-stabilized absorbent structure was formed inaccordance with the absorbent structure illustrated in FIG. 10, having acentral region of increased thickness intermediate the side edges andlongitudinal ends of the absorbent structure. The central region of theabsorbent structures so formed measured 7.6 cm wide in the crotch regionby 21.6 cm in length. Materials utilized were 50% SXM 9543superabsorbent (a superabsorbent material available from Stockhausen,Inc.) and 50% CR-1654 pulp (available from Bowater, Inc., Greenville,S.C.). The central region had a basis weight of 1200 gsm with all otherregions of the absorbent structure having a basis weight of 300 gsm. Theabsorbent structure was densified in a Carver press, Model No. 4531, andavailable from Carver, Inc., a business having offices in Wabash, Ind.,U.S.A., using 0.1 inch shims and 20000 pounds of pressure for 90seconds. Each sample of the absorbent structure of this Example wassubjected to the Cylindrical Compression Test described below.

Example 2

In this Example, a non-stabilized absorbent structure was formed in amanner similar to that of Example 1. In this Example, however, a formedgrid approximately 20.3 cm long and approximately 7.6 cm wide consistingof two wall segments running in the longitudinal direction spacedapproximately 2.5 cm apart and eight wall segments running in thetransverse width direction spaced approximately 2 cm apart were placedin a foraminous member similar to that illustrated in FIG. 10. Theformed grid had walls approximately 0.85 mm thick and approximately 6 cmhigh. The entire formed grid was raised approximately 0.7 cm off thefloor of the foraminous member and was similar in appearance to thatillustrated in FIG. 13. Materials utilized were 50% SXM 9543superabsorbent and 50% CR-1654 pulp. The central region had a basisweight of 1200 gsm with all other regions of the absorbent structurehaving a basis weight of 300 gsm. The absorbent structure was densifiedin the Carver press using 0.1 inch shims and 20000 pounds of pressurefor 90 seconds. Each sample of the absorbent structure of this Examplewas subjected to the Cylindrical Compression Test described below.

Example 3

In this Example, a non-stabilized absorbent structure was formed in amanner similar to that of Example 1. In this Example, however, a gridwas formed by compressing a wire mesh onto the formed absorbentstructure. The wire grid was formed from 2.5 mm OD copper coated weldingrods and was similar in appearance to that illustrated in FIG. 14. Thewire grid was otherwise similar in its spacing to that of the formedgrid previously described in Example 2. The wire grid was placed on theupper or bodyfacing surface of the absorbent structure. 2000 pounds ofpressure were exerted on the wire grid for about 60 seconds in theCarver press. Materials utilized were 50% SXM 9543 superabsorbent and50% CR-1654 pulp. The central region had a basis weight of 1200 gsm withall other regions of the absorbent structure having a basis weight of300 gsm. The absorbent structure was densified in the Carver press using0.1 inch shims and 20000 pounds of pressure for 90 seconds. Each sampleof the absorbent structure of this Example was subjected to theCylindrical Compression Test described below.

Example 4

In this Example, a stabilized absorbent structure was formed inaccordance with the absorbent structure illustrated in FIG. 10, having acentral region of increased thickness intermediate the side edges andlongitudinal ends of the absorbent structure. The central region of theabsorbent structures so formed measured 7.6 cm wide in the crotch regionby 21.6 cm in length. Materials utilized were 45% SXM 9543superabsorbent, 50% CR-1654 pulp and 5% T-255 binder fiber, a binderfiber available from KoSa, a business having offices in Houston, Tex.,U.S.A. The central region had a basis weight of 1200 gsm with all otherregions of the absorbent structure having a basis weight of 300 gsm. Thesamples were stabilized by placing in a convective oven and heating forsix minutes at 170° C. Following stabilization, the absorbent structurewas densified in the Carver press using 0.1 inch shims and 20000 poundsof pressure for 90 seconds. Each sample of the absorbent structure ofthis Example was subjected to the Cylindrical Compression Test describedbelow.

Example 5

In this Example, a stabilized absorbent structure was formed in a mannersimilar to that of Example 4. In this Example, however, a formed gridapproximately 20.3 cm long and approximately 7.6 cm wide consisting oftwo wall segments running in the longitudinal direction spacedapproximately 2.5 cm apart and eight wall segments running in thetransverse width direction spaced approximately 2 cm apart were placedin a foraminous member similar to that illustrated in FIG. 10. Theformed grid had walls approximately 0.85 mm thick and approximately 6 cmhigh. The entire formed grid was raised approximately 0.7 cm off thefloor of the foraminous member and was similar in appearance to thatillustrated in FIG. 13. Materials utilized were 45% SXM 9543superabsorbent, 50% CR-1654 pulp and 5% T-255 (0.25 inch) binder fiber.The central region had a basis weight of 1200 gsm with all other regionsof the absorbent structure having a basis weight of 300 gsm. The sampleswere stabilized by placing in a blue convective oven and heating for sixminutes at 170° C. Following stabilization, the absorbent structure wasdensified in the Carver press using 0.1 inch shims and 20000 pounds ofpressure for 90 seconds. Each sample of the absorbent structure of thisExample was subjected to the Cylindrical Compression Test describedbelow.

Example 6

In this Example, a stabilized absorbent structure was formed in a mannersimilar to that of Example 4. In this Example, however, a grid wasformed by compressing a wire mesh onto the formed absorbent structure.The wire grid was formed from 2.5 mm OD copper coated welding rods andwas similar in appearance to that illustrated in FIG. 14. The wire gridwas otherwise similar in its spacing to that of the formed gridpreviously described in Example 5. The wire grid was placed on the upperor bodyfacing surface of the absorbent structure. 2000 pounds ofpressure were exerted on the wire grid for about 60 seconds in theCarver press. Materials utilized were 45% SXM 9543 superabsorbent, 50%CR-1654 pulp and 5% T-255 (0.25 inch) binder fiber. The central regionhad a basis weight of 1200 gsm with all other regions of the absorbentstructure having a basis weight of 300 gsm. The samples were stabilizedby placing in a blue convective oven and heating for six minutes at 170°C. Following stabilization, the absorbent structure was densified in theCarver press using 0.1 inch shims and 20000 pounds of pressure for 90seconds. Each sample of the absorbent structure of this Example wassubjected to the Cylindrical Compression Test described below.

Cylindrical Compression Test

The Cylindrical Compression values of the foregoing Examples wereevaluated. As used herein, the Cylindrical Compression Value is ameasure of the dry stiffness (or flexibility) of the absorbent material.The method by which the value for edge-wise or cylindrical compressioncan be determined is set forth in U.S. Pat. No. 6,323,388.

A 3 inch by 12 inch (7.6 cm×30.5 cm) piece of absorbent material (orproduct) was cut for each example, with the longer dimension alignedwith the longitudinal direction of the product or raw material web. Theexample piece was formed into a cylinder having a height of 3 inches(7.6 cm), and with the two ends having 0-0.125 inch (0-3.18 mm) overlap,the sample is stapled together with three staples. One staple was nearthe middle of the width of the example, the other two nearer each edgeof the width of the sample. The longest dimension of the staple was inthe circumference of the formed cylinder to minimize the effect of thestaples on the testing.

A Sintech tester, or similar instrument was configured with a bottomplatform, a platen larger than the circumference of the sample to betested and parallel to the bottom platform, attached to a compressionload cell placed in the inverted position. The specimen was placed onthe platform, under the platen. The platen was brought into contact withthe specimen and compressed the sample to 50% of its width at a rate of25 mm/min. The force at yield obtained in compressing the sample to 50%of its width (1.5 inches) (3.8 cm) was recorded. In addition, the energyrequired to compress each example to 50% of its width was recorded.

In an example where the length of the absorbent is less than 12 inches(30.5 cm), the Cylindrical Compression Value of the material can yet bedetermined. A detailed discussion of the cylindrical or edge-wisecompression strength has been given in The Handbook Of Physical AndMechanical Testing Of Paper And Paperboard, Richard E. Mark editor,Dekker 1983, (Vol. 1). As discussed therein, for the CylindricalCompression configuration described, the buckling stress is proportionalto E*t²/(H²), with the proportionality constant being a function ofH²/(R*t) where E is the Elastic modulus, H is the height of thecylinder, R is the radius of the cylinder, and t is the thickness of thematerial. When expressing the stress in terms of force per basis weight,the parameter that needs to remain constant is H²/R. Therefore, for asample that is smaller than 12 inches (30.5 cm), the largest possiblecircle should be constructed and its height (width of the sample beingcut out) adjusted such that H²/R equals 2.1 inches (5.3 cm).

Each of the samples prepared according to the foregoing Examples wassubjected to the Cylindrical Compression Test. The average values arereported in the following Table. Density Energy to 50% Load at YieldExample (g/cm³) (gf*mm) (gf) 1 0.212 38179 1291 2 0.184 18381 517 30.213 36249 1208 4 0.131 59774 1438 5 0.136 39162 1010 6 0.130 409101138

The foregoing values indicate that a non-stabilized absorbent structurehaving discontinuous absorbent zones as in Example 2, has a cylindricalcompression load at yield that is at least 60 percent less than thecylindrical compression load at yield of an otherwise similarnon-stabilized absorbent structure free of discontinuous absorbent zonesas in Example 1. Moreover, the stabilized absorbent structure havingdiscontinuous absorbent zones as in Example 5, has a cylindricalcompression load at yield that is at least 30 percent less than thecylindrical compression load at yield of an otherwise similar stabilizedabsorbent structure free of discontinuous absorbent zones as in Example4.

It will be appreciated that details of the foregoing versions, given forpurposes of illustration, are not to be construed as limiting the scopeof this invention. Although only a few versions of this invention havebeen described in rather full detail, those skilled in the art willreadily appreciate that many modifications are possible in the variousversions without materially departing from the novel teachings andadvantages of this invention. For example, features described inrelation to one version may be incorporated into any other version ofthe invention.

Accordingly, all such modifications are intended to be included withinthe scope of this invention, which is defined in the following claimsand all equivalents thereto. Further, it is recognized that manyversions may be conceived that do not achieve all of the advantages ofsome of the versions, yet the absence of a particular advantage shallnot be construed to necessarily mean that such a version is outside thescope of the present invention.

When introducing elements of the present invention, the articles “a”,“an”, “the” and “said” are intended to mean that there are one or moreof the elements. The terms “comprising”, “including” and “having” areintended to be inclusive and mean that there may be additional elementsother than the listed elements.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1. An absorbent body suitable for incorporation into disposableabsorbent articles, the absorbent body comprising: a non-woven absorbentstructure having a unitary construction and comprising absorbent fibers,the absorbent structure having a longitudinal length, a lateral widthand a thickness, a portion of the absorbent structure havingdiscontinuous absorbent zones that define at least two channels, atleast one of the channels running in a longitudinal length direction andat least one of the channels running in a lateral width direction, andwherein the density of the absorbent structure in the channels is lessthan or equal to the density of a portion of the absorbent structureadjacent the channels.
 2. The absorbent body of claim 1, wherein thatportion of the absorbent structure having the discontinuous absorbentzones has a cylindrical compression at yield which is at least 55percent less than the cylindrical compression at yield of an otherwisesimilar absorbent structure free of the discontinuous absorbent zones.3. The absorbent body of claim 2, wherein the channels extend through noless than 10 percent of the thickness of the absorbent structure; andwherein the channels extend through no more than 90 percent of thethickness of the absorbent structure.
 4. The absorbent body of claim 3,wherein the at least one channel running in a longitudinal lengthdirection extends no less than 20 percent of the longitudinal length ofthe absorbent structure.
 5. The absorbent body of claim 3, wherein theat least one channel running in a lateral width direction extends noless than 20 percent of the lateral width of the absorbent structure. 6.The absorbent body of claim 1, wherein the absorbent structure furthercomprises binder material activated to form inter-fiber bonds within theabsorbent structure.
 7. The absorbent body of claim 6, wherein thatportion of the absorbent structure having the discontinuous absorbentzones has a cylindrical compression load at yield which is at least 30percent less than the cylindrical compression load at yield of anotherwise similar absorbent structure free of the discontinuousabsorbent zones.
 8. The absorbent body of claim 7, wherein the channelsextend through no less than 10 percent of the thickness of the absorbentstructure; and wherein the discrete channels extend through no more than90 percent of the thickness of the absorbent structure.
 9. The absorbentbody of claim 8, wherein the at least one channel running in alongitudinal length direction extends no less than 20 percent of thelongitudinal length of the absorbent structure.
 10. The absorbent bodyof claim 8, wherein the at least one channel running in a lateral widthdirection extends no less than 20 percent of the lateral width of theabsorbent structure.
 11. An absorbent article comprising a fluidpervious liner, a liquid impervious outer cover and an absorbent bodydisposed between the liner and the outer cover, the absorbent bodycomprising: a non-woven absorbent structure having a unitaryconstruction and comprising absorbent fibers, the absorbent structurehaving a longitudinal length, a lateral width and a thickness, andwherein a portion of the absorbent structure has discontinuous absorbentzones that define at least two discrete channels and wherein the densityof the absorbent structure in the discrete channels is less than orequal to the density of a portion of the absorbent structure adjacentthe discrete channels.
 12. The absorbent body of claim 11, wherein thatportion of the absorbent structure having the discontinuous absorbentzones has a cylindrical compression at yield which is at least 55percent less than the cylindrical compression at yield of an otherwisesimilar absorbent structure free of the discontinuous absorbent zones.13. The absorbent body of claim 12, wherein the channels extend throughno less than 10 percent of the thickness of the absorbent structure; andwherein the channels extend through no more than 90 percent of thethickness of the absorbent structure.
 14. The absorbent body of claim13, wherein the at least one channel running in a longitudinal lengthdirection extends no less than 20 percent of the longitudinal length ofthe absorbent structure.
 15. The absorbent body of claim 13, wherein theat least one channel running in a lateral width direction extends noless than 20 percent of the lateral width of the absorbent structure.16. The absorbent body of claim 11, wherein the absorbent structurefurther comprises binder material activated to form inter-fiber bondswithin the absorbent structure.
 17. The absorbent body of claim 16,wherein that portion of the absorbent structure having the discontinuousabsorbent zones has a cylindrical compression load at yield which is atleast 30 percent less than the cylindrical compression load at yield ofan otherwise similar absorbent structure free of the discontinuousabsorbent zones.
 18. The absorbent body of claim 17, wherein thechannels extend through no less than 10 percent of the thickness of theabsorbent structure; and wherein the discrete channels extend through nomore than 90 percent of the thickness of the absorbent structure. 19.The absorbent body of claim 18, wherein the at least one channel runningin a longitudinal length direction extends no less than 20 percent ofthe longitudinal length of the absorbent structure.
 20. The absorbentbody of claim 18, wherein the at least one channel running in a lateralwidth direction extends no less than 20 percent of the lateral width ofthe absorbent structure.
 21. An absorbent body suitable forincorporation into disposable absorbent articles, the absorbent bodycomprising: a non-woven absorbent structure having a unitaryconstruction and comprising absorbent fibers, the absorbent structurehaving a longitudinal length, a lateral width and a thickness, a portionof the absorbent structure having discontinuous absorbent zones thatdefine at least four channels, at least two of the channels being spacedfrom one another and running in a longitudinal length direction, atleast two of the channels being spaced from one another and running in alateral width direction, the portion of the absorbent structure havingthe discontinuous absorbent zones having a cylindrical compression loadat yield which is at least 55 percent less than the cylindricalcompression load at yield of an otherwise similar absorbent structurefree of the discontinuous absorbent zones, and wherein the density ofthe absorbent structure in the channels is less than or equal to thedensity of a portion of the absorbent structure adjacent the channels.22. The absorbent body of claim 21, wherein the channels extend throughno less than 10 percent of the thickness of the absorbent structure; andwherein the channels extend through no more than no more than 90 percentof the thickness of the absorbent structure.
 23. The absorbent body ofclaim 22, wherein the channels running in a longitudinal lengthdirection extend no less than 20 percent of the longitudinal length ofthe absorbent structure.
 24. The absorbent body of claim 22, wherein thechannels running in a lateral width direction extend no less than 20percent of the lateral width of the absorbent structure.
 25. Theabsorbent body of claim 21, wherein the absorbent structure furthercomprises binder material activated to form inter-fiber bonds within theabsorbent structure.
 26. The absorbent body of claim 25, wherein thatportion of the absorbent structure having the discontinuous absorbentzones has a cylindrical compression load at yield which is at least 30percent less than the cylindrical compression load at yield of anotherwise similar absorbent structure free of the discontinuousabsorbent zones.
 27. The absorbent body of claim 26, wherein thechannels extend through no less than 10 percent of the thickness of theabsorbent structure; and wherein the channels extend through no morethan 90 percent of the thickness of the absorbent structure.
 28. Theabsorbent body of claim 27, wherein the channels running in alongitudinal length direction extend no less than 20 percent of thelongitudinal length of the absorbent structure.
 29. The absorbent bodyof claim 27, wherein the channels running in a lateral width directionextend no less than 20 percent of the lateral width of the absorbentstructure.